Very slow seedling growth in nearly perfect setup??

Hey guys,
I have grown a few times before and the plants tended to get onto their 3rd or 4th set of leaves by 2 weeks age. I recently moved to a different country with a new setup and now my seedlings are growing ridiculously slowly.. This is at 2 weeks age (as of today).


Temp= 80-84.7 Fahrenheit (27-29 Celsius)
lights= 400w mh, 16 inches away from seedling
humidity= only 20% (is the slow growth due to this??)
ventilation= oscillating fan and good air change
soil= 25% vermiculite, 25% perlite, 50% some store soil that should be alright but not sure.. (i miss ffof..)

The plant looks completely healthy but there is barely any growth day after day.. I was thinking of giving it 1/4 nutes in a couple of days to see if that would help.. My other seedlings started growth slow too but this one is even slower. what the hell is going on/wrong with my setup?!?

I would normally say let it chill out for a few days, but yours has already begun to exhaust it's cotyledon's, so I would say yes feed but start with 1/8 strength but focus on root development. Even if she takes a bit longer than normal, once the roots are boomin then she will show you in bloom. humidity is supposed to be higher 60-80. raise your light you are stunting it. 400 seedlings= 30" lower temp to 75f

I dont know where you are getting 30" for a 400w for a seedling from? I try to keep them closer to 8 or 10".

You are a little too hot, and I agree, too dry. I'm having a dryness issue as well and am also experiencing slow growth at all growth stages so I think that's probably it.

ProdigalSun said:

I dont know where you are getting 30" for a 400w for a seedling from? I try to keep them closer to 8 or 10".

You are a little too hot, and I agree, too dry. I'm having a dryness issue as well and am also experiencing slow growth at all growth stages so I think that's probably it.

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Honestly dont know how much I can lower the temp though, I ordered a new vortex fan with higher cfm but not sure about how it will affect temp.I have a bucket in the grow room but it hasn't increased humidity at all. Honestly if I cant pin down any other reason, I will definitely buy a humidifier (really dont wanna pay more due to how expensive the setup is already and im growing only for personal use)..

tikitoker said:

I would normally say let it chill out for a few days, but yours has already begun to exhaust it's cotyledon's, so I would say yes feed but start with 1/8 strength but focus on root development. Even if she takes a bit longer than normal, once the roots are boomin then she will show you in bloom. humidity is supposed to be higher 60-80. raise your light you are stunting it. 400 seedlings= 30" lower temp to 75f

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Thanks for the quick reply mate,
ill start at 1/8th tomorrow (need to let it dry off a bit). Its probably focusing on root dev and then it will explode into growth, just not used to it doing this process so slowly so id like to try to figure out whats different/wrong with this setup.. I might try to move it under my 125w cfl, later today, to see if the mh was stunting it.

What are your temps outside, it's winter here. Are you taking air into the room or exhausting out? Have you thought about those cool tubes? They solve a lot of heat issues for people, myself included.

ProdigalSun said:

What are your temps outside, it's winter here. Are you taking air into the room or exhausting out? Have you thought about those cool tubes? They solve a lot of heat issues for people, myself included.

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Temp in the room is about 73 Fahrenheit (23c), exhausting directly out into a vent going outside. Outside its 14f but cant vent that in reasonably without making my apartment freezing cold. I used to have a cool tube type of fixture and it was awesome, but can't afford it this time around..

ProdigalSun said:

I dont know where you are getting 30" for a 400w for a seedling from? I try to keep them closer to 8 or 10".

You are a little too hot, and I agree, too dry. I'm having a dryness issue as well and am also experiencing slow growth at all growth stages so I think that's probably it.

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Sorry. His seedling is 2+ weeks and 2" tall, there is something not right about blasting a unhealthy stunted seedling with a 400 at 8". LOL dude your asking for problems and temps are already at 84f. Raise the light and watch for stretch, If there stunted and not growing what the hell do they need light for, they will eventually bounce back and that's when they need the light, so then in that case I would be inclined to agree with the 10" ONLY if temps were controlled. Here is a pic of my seedlings that are 16 days old and have been topped from node7 down to 3.

tikitoker said:

Sorry. His seedling is 2+ weeks and 2" tall, there is something not right about blasting a unhealthy stunted seedling with a 400 at 8". LOL dude your asking for problems and temps are already at 84f. Raise the light and watch for stretch, If there stunted and not growing what the hell do they need light for, they will eventually bounce back and that's when they need the light, so then in that case I would be inclined to agree with the 10" ONLY if temps were controlled. Here is a pic of my seedlings that are 16 days old and have been topped from node7 down to 3.

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Just out of curiosity, what is your humidity?

Tamuuli said:

Temp in the room is about 73 Fahrenheit (23c), exhausting directly out into a vent going outside. Outside its 14f but cant vent that in reasonably without making my apartment freezing cold. I used to have a cool tube type of fixture and it was awesome, but can't afford it this time around..

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Room temp is good. You might be suprised how much an 80cfm computer fan will do for a small grow area. All you need to do is come down a few degrees and a smaller fan will do that without freezing you out of house or home.

I have never fried a seedling by getting it within a foot or so of a light. Just out of curiosity, how do you know this? A plant too far away from the light will stretch, but I just had a Tutankhuman stretch at a foot from the 400.

A sprout popped a couple hours ago, I'm going to go put it under the 1,000w HPS about a foot or so away and I'm not really worried even though there are only 2 weeks on the bulb and ballast.

It is all about the ferts. Could be too much or too little. We would need to know more about the soil you got from the store. Seedlings actually do much better with a small bit of ferts. If you get it just right your cotyledons will actually grow larger and stay green.

My current Pineapple Kush stayed at the seedling stage for 31 days before it exploded in growth. I have no clue why it did this. But looking around the internet, I found that this happens now and again. Be patient and no nutes. Let it go, it will start to grow and when it does its gonna take off.

Tamuuli said:

Just out of curiosity, what is your humidity?

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First 3 days out of the prop in veg room rh is at 70.
Over next 4 days I drop it to 60 and maintain it untill day 12.
Day 13 it drops to 54-55 and stays there untill I flower.
Flower rh is 40-45 temp 68-70f

Using new tap water or bottled/distilled?

tikitoker said:

First 3 days out of the prop in veg room rh is at 70.
Over next 4 days I drop it to 60 and maintain it untill day 12.
Day 13 it drops to 54-55 and stays there untill I flower.
Flower rh is 40-45 temp 68-70f

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I raised the light a few inches to lower temp (until my vortex fan comes), and ordered a humidifier which should be here tomorrow or friday. Ill let you guys know what happens

twostrokenut said:

Using new tap water or bottled/distilled?

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tap water that I let sit out for a day

Tamuuli said:

I raised the light a few inches to lower temp (until my vortex fan comes), and ordered a humidifier which should be here tomorrow or friday. Ill let you guys know what happens

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temp is now at ~78-79f

high ph/ over watered/ or cold temps is my guess..... proabably the soil has alot to do with it, looks like it sucks

I had the same thing happen to me. 4wk and only 2 leaves turned the light off for 24hr then back on it took right off after that. hope this helps

Tamuuli said:

tap water that I let sit out for a day

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What's the pH of the water?