Rust Spots Turning Into Brittle Yellow/Brown Leaves.

[Pimpernickel]

The leaves at the top of a few of my plants start to get light rust colored brown spots which become numerous brown spots and the entire leaf yellows and crisps up a bit. They're about 12" under a 1KW HPS, I have RO water and use House & Garden nutes according to their soil feeding schedule. The last leaf is a bit different than most and it's not at the top of the canopy but I attached it anyway just incase it helps. My last grow suffered this same problem which affected every top leaf that was under the light, the stuff on the edges of the grow didn't have the problem but they also didn't produce well because they weren't getting much light. I'm using FF Happy frog soil, my leaf temp is ~86 degrees @1000ish PPM. What's causing this? Can my light do that to them?

 

[420God]

Magnesium deficiency, get some cal/mag+ or Epsom salt.

 

[Pimpernickel]

I put gave it cal/mag the last few feedings, not last week though, the guy at the hydro shop said the H&G has plenty cal/mag in it. I'm using RO water pH 6.2, which I check after adding my base nutes. Could I be getting lockout from something I'm not thinking of? Also, why wouldn't I see it on the plants not under the lights?

 

[smokebros]

look for new growth, not the existing shit

 

[Tricks]

Check Run off PH

 

[Rippedvanwinkle77]

When you water them do you ever let water drain through the bottom of the pot? It looks like it may need a flush.

 

[a mongo frog]

h&g soil A and B dosent have the cal mg your looking for. its the coco A and B that has the cal mg in it. for soil A and B its a must that 2 straight waterings have cal mg in the mix. usally in week 2 of flowering is when this is added. hope this helps.

 

[Pimpernickel]

Thanks for the responses, some questions.
Tricks: What does checking the run-off pH tell me? I have checked it before because I think I killed a plant reusing runoff nutes, usually measures a lot lower than I put it in.
Rip: They get fed w/ about 1 gallon of nutes per week, if I have extra I use it to create run-off. They are also straight watered mid week until run-off.
Mongo: Are you saying that two watering be they feed or water should have a cal/mag does or once every other non feed? What should I be dosing at the instructions are fairly loose.

 

[thegreensurfer]

all this talk about mg deficiency is nonsense. its overfed or salt buildup.
Whats kind of soil? How big is your container?

 

[Pimpernickel]

FF Happy Frog 7 gallons.

 

[420God]

FF Happy Frog 7 gallons.

To eliminate any question of the lockout or build up, give your plants a good flush before adding anything or making any changes.

When in doubt, flush and start fresh.

 

[cannabisguru]

here, here's a nice chart for everyone to check out. Not sure how accurate the chart is.. but its def. a good chart IMO. But again, as for the accuracy of it.. not sure on that.. because I didn't create the chart. But here it is.. if anyone wants it.

View attachment 1498834

 

[a mongo frog]

what week r u on ? r u aggresive strength or normal ? if your using drip clean i doubt its salt build up. have u done any magic greening yet. if not u should. the guy who said over fed might have a point. if im corect happy frog comes with alot of ferts in soil, so u wouldnt have to feed with nutes right away. but that depends did u veg in the same soil and containers ? im against flushing with h&g because of drip clean, but if there over fed u should.

 

[Tricks]

Tricks: What does checking the run-off pH tell me? I have checked it before because I think I killed a plant reusing runoff nutes, usually measures a lot lower than I put it in.

It tells you if your soil is PH stable. As someone mentioned here already, a flush might be good, but flush it with the right PH. Keep your runoff in the 6-7 range, keep flushing till your there.

The rust spots usually indicate PH fluctuation.

 

[steverthebeaver81]

its a potassium deficiency. and probably magnesium too.
View attachment 1499133

 

[Pimpernickel]

what week r u on ? r u aggresive strength or normal ? if your using drip clean i doubt its salt build up. have u done any magic greening yet. if not u should. the guy who said over fed might have a point. if im corect happy frog comes with alot of ferts in soil, so u wouldnt have to feed with nutes right away. but that depends did u veg in the same soil and containers ? im against flushing with h&g because of drip clean, but if there over fed u should.

Week 5, the problem doesn't normal strength. I use drip clean and just started using magic green. I see very few light rust spots during veg then midway through flower it hits the tops of the plants under the light(the larger ones).

 

[Pimpernickel]

It tells you if your soil is PH stable. As someone mentioned here already, a flush might be good, but flush it with the right PH. Keep your runoff in the 6-7 range, keep flushing till your there.

The rust spots usually indicate PH fluctuation.

I haven't checked my runoff recently but I have in the past and it's always waay lower than the 6.2 water and feed I'm putting in.

 

[Tricks]

I haven't checked my runoff recently but I have in the past and it's always waay lower than the 6.2 water and feed I'm putting in.

Check your runoff and adjust your PH, all problems have a source.

 

[Pimpernickel]

its a potassium deficiency. and probably magnesium too.
View attachment 1499133

I'm pretty sure it's not K, it doesn't look like any of the real life pictures I've seen of it and the problem doesn't start on the outer edges of the leaf.

I am thinking whatever problem they have it's being compounded by heat stress or bleaching, I think that's causing some of the yellowing but the spots I'm not sure about.

 

[Tricks]

Runoff needs to be in the 6-7PH range with soil or it will cause all kinds of lockouts.