What are these brown spots on fan leaves?

G'day all, I am just wondering what these brown spots are on my fan leaves. The spots are only on a few of the leaves, the leaves next to the ones with spots don't have them at all. Is it a calcium deficiency possibly? I've been giving calmag once a week but only a low dose because I accidentally over fed them and gave them nute burn over a week ago and at the same time they outgrew the tent I had so I had to buy another one so they also had light stress from that too. Didn't expect autoflowers to grow so tall. They are at 10 weeks. If anyone could help me out on what this is will be much appreciated. Thanks very much

Post a picture of the entire plant and not just individual leaves. Plus some grow details because it’s important in trying to determine what is going on.

In the meantime read about phosphorus deficiency in cannabis.

hotrodharley said:

In the meantime read about phosphorus deficiency in cannabis.

Click to expand...

Thankyou for getting back so quick. They are white widow autoflower cbd. I'm growing in Ugrow Coco perlite in mesh pots and I'm using professor's original nutrients A&B, professor's flower boost, bio deisel marine calmag. They are under mars hydro ts600 led light (think I need a stronger one possibly.) Unfortunately I don't have an EC meter yet but I'm getting one soon so I've really been winging it with nutrients since they have been in flower because the nutrients I have seem to be very high in nitrogen. I do have a pH metre which I have been using to keep the nutrient solution at pH5.9 - 6.0. I did try to read the runoff of the Coco but I realised pretty quickly you can't get a proper runoff reading from Coco. I have also been having trouble with humidity as it's very humid in Melbourne at the moment so I've been battling that big time too. I have managed to get the humidity down to 60 - 65% and because the humidity is so high the temp is a bit low at 20 degrees celsius from having the fans on high. The humidity did get up to 90% at one point. I've got the inline fan, oscillating fan & mini dehumidifier. I did find a few whiteflies and there was white spots on the leaves so I have treated them twice with eco oil & eco fungicide mixed together and I did use eco neem but only once before I figured out that I'd need the fungicide & miticide. One plant is quite light green too and the other is darker green but they are different ages, one is at 10 weeks and the other is at 9 weeks. The darker green one is the 10 week old. Hopefully that makes it easier to figure out what the spots are. The spots are pretty uniform too and only on the top of the leaf. I'll read up on Phosphorus now. Thankyou very much for helping me out with this, I've been struggling lately with what's going on.

hotrodharley said:

In the meantime read about phosphorus deficiency in cannabis.

Click to expand...

Here's more pictures.

Are you using ro water?
Id bet on the fact you're using calmag at a high dose and you don't need to use it at all, causing a lock out. I'd ditch the calmag.

Jjgrow420 said:

Are you using ro water?
Id bet on the fact you're using calmag at a high dose and you don't need to use it at all, causing a lock out. I'd ditch the calmag.

Click to expand...

Okay ditching the calmag. I'm using tap water that I let sit in an open container for 24 hours to let the chlorine and stuff evaporate but sometimes I'm lazy and just use tap water straight from the tap. While I've got you, do you know what this bug is? Also there's little white egg like things on some fan leaves too, I can't seem to rid the little shits. Thanks heaps for your advice! Will be getting ec meter in the next week, I'm hopeful it will make nutrients much easier.

BibbyMcBuds said:

Okay ditching the calmag. I'm using tap water that I let sit in an open container for 24 hours to let the chlorine and stuff evaporate but sometimes I'm lazy and just use tap water straight from the tap. While I've got you, do you know what this bug is? Also there's little white egg like things on some fan leaves too, I can't seem to rid the little shits. Thanks heaps for your advice! Will be getting ec meter in the next week, I'm hopeful it will make nutrients much easier.

Click to expand...

Hey np man. Pic is pretty blurry it's really hard to tell what it could be.
Nothing wrong with tap water.
Only reason I'd use calmag is if I was using ro water or my nutes didn't have enough calcium (which most do)

Jjgrow420 said:

Hey np man. Pic is pretty blurry it's really hard to tell what it could be.
Nothing wrong with tap water.
Only reason I'd use calmag is if I was using ro water or my nutes didn't have enough calcium (which most do)

Click to expand...

That makes sense thanks for that. I actually was using spring water at the start of the grow with the calmag so thinking back when I changed to tap water I should have stopped the calmag. Yeah the bug is so small it was hard to get a picture of it plus they like bounce around. I'm still trying to find what bug it is, do you think it could be a thrip maybe?

BibbyMcBuds said:

That makes sense thanks for that. I actually was using spring water at the start of the grow with the calmag so thinking back when I changed to tap water I should have stopped the calmag. Yeah the bug is so small it was hard to get a picture of it plus they like bounce around. I'm still trying to find what bug it is, do you think it could be a thrip maybe?

Click to expand...

It's a springtail.

I use tap water, and don't really add much calmag, since it is already in the city water and in my flower nutes. Hotrod is right. you may have thrown off ph causing phosphorus deficiencies. Magnesium I've heard is neutral on ph, but the calcium nitrate can raise your ph.

mag is neutral on ph, but problem is calcium nitrate. I am same... I use tap water and calmag sparingly. I do see your purpling stems. Some strains are calmag hogs, like OG Kush. The darkening around the veins in one pic of the leaf is due to ph imbalance. Basically your having some lock out. Plant looks good overall, with some stress. Use the flowering nute mix 0-4-4/ph'd, most already have mag as an element.

some one else was posting an issue with same bug... slendor springtale... attracted to overwatering. suggested nematodes.

Mericat said:

It's a springtail.

Click to expand...

Thankyou much appreciated. Don't know why springtails aren't on the usual suspect pest list, was starting to wonder if it was a baby thrip but that didn't make sense coz it doesn't have wings.

thcscreener said:

mag is neutral on ph, but problem is calcium nitrate. I am same... I use tap water and calmag sparingly. I do see your purpling stems. Some strains are calmag hogs, like OG Kush. The darkening around the veins in one pic of the leaf is due to ph imbalance. Basically your having some lock out. Plant looks good overall, with some stress. Use the flowering nute mix 0-4-4/ph'd, most already have mag as an element.

some one else was posting an issue with same bug... slendor springtale... attracted to overwatering. suggested nematodes.

Click to expand...

Thankyou very much for your advice, much appreciated. They are white widow auto CBD strain. I did think it could be pH imbalance in the Coco and tried to test run off but realised testing Coco runoff is inaccurate. So do you think I should flush then just use the flower boost nutes from now on? They are 9 and 10 weeks, the npk on my flower nutes is 0-10-8.7. No nitrogen which is why I was adding the A&B nutes in small amounts to add nitrogen to the mix but without an EC meter I've been winging it. I'm getting the EC meter tomorrow to get it to the recommended value. Do you think they still need nitrogen at this stage? Thanks again

thcscreener said:

mag is neutral on ph, but problem is calcium nitrate. I am same... I use tap water and calmag sparingly. I do see your purpling stems. Some strains are calmag hogs, like OG Kush. The darkening around the veins in one pic of the leaf is due to ph imbalance. Basically your having some lock out. Plant looks good overall, with some stress. Use the flowering nute mix 0-4-4/ph'd, most already have mag as an element.

some one else was posting an issue with same bug... slendor springtale... attracted to overwatering. suggested nematodes.

Click to expand...

I'll have a look at those nematodes now, never heard of them. I'm growing in Coco so yeah I have to keep it very moist otherwise it dries out too much. I've been told time and time again that you can't overwater in Coco but I'm assuming the bugs love the constantly wet conditions