Please help. Rapid deterioration on lower leaves, light spots w/ black edges.

Hey everyone, this morning I woke up and noticed some light spots on a few of the leaves. I'm running FFOF, this is day 22 from sprout. I applied my very first nutes today, cal mag and 1/3 dose of FF grow big. I was told to wait till 21 days to apply anything since FFOF is pretty hot.

So over the course of today, it has rapidly deteriorated into what you see in the photos... Under my 45x lighted glass I see no bugs however on the underside, the light spot edges appear to have a black edge. This morning they just looked like light spots, some lighter than others but now they are looking much worse.

Any ideas what this can be? I've searched for green spots and black spots, I can't find anything where there is green spots with black edges underneath that ultimately just destroys the tissue as seen in the third image. The only thing that I've found that is even close is calcium deficiency which could make sense since I've applied nothing but jesh, would it go downhill this fast?

Here is my current setup for reference:

Soil: FFOF
Age: 22 days since sprout
Nutes: First time was today. CalMag + 1/3 dose of FF grow big. PPM w/ water was 588.
Water Regime: About 1.5 x per week of 6.2-6.5 PH'd water
Pots: 3G Smart Pots
Lighting: 6x 50W Cree CXB3590
Environmental Variables: It has been very hot and humid. That has been addressed within the last 48 hours with a dehumidifier and dialing down the lights.

Did you splash anything on them whilst feeding?...

@sworth I did actually. I didn't even think to mention this. Today was the first day of applying anything outside of water but in my first feed excitement, it didn't even dawn on me to be more careful. Most of the lower leaves got splashed so I just gently jostled the leaves a bit and tapped the stalks. Upon further research it looks like cal deficiencies can be seen in new growth first yet my symptoms are only showing up to about 4" on the plants which is my prime splash zone hah. Here I am thinking I've got a case of instantaneous deficiencies, tobacco mosaic virus, god smiting, zobmies bit them, the whole shebang.

I wholeheartedly thank you for taking the time man. I'll monitor them to see if the issue rises to higher nodes.

slow_grow said:

Hey everyone, this morning I woke up and noticed some light spots on a few of the leaves.

Environmental Variables: It has been very hot and humid. That has been addressed within the last 48 hours with a dehumidifier and dialing down the lights.

Click to expand...

The dehum is drying out the air, and blowing dry air on your plants, which acts like a desiccate .
If it happened today...
and you have added the dehum in the last two days, logic would lead you to believe the biggest variable (especially when dry-spots are the damage) is the dehum.
that's my educated guess

slow_grow said:

@sworth I did actually. I didn't even think to mention this. Today was the first day of applying anything outside of water but in my first feed excitement, it didn't even dawn on me to be more careful. Most of the lower leaves got splashed so I just gently jostled the leaves a bit and tapped the stalks. Upon further research it looks like cal deficiencies can be seen in new growth first yet my symptoms are only showing up to about 4" on the plants which is my prime splash zone hah. Here I am thinking I've got a case of instantaneous deficiencies, tobacco mosaic virus, god smiting, zobmies bit them, the whole shebang.

I wholeheartedly thank you for taking the time man. I'll monitor them to see if the issue rises to higher nodes.

Click to expand...

was it PURE nutrients that were splashed on them? Un-diluted nutrients could do that..
if it was water that's not going to do that

greasemonkeymann said:

The dehum is drying out the air, and blowing dry air on your plants, which acts like a desiccate .
If it happened today...
and you have added the dehum in the last two days, logic would lead you to believe the biggest variable (especially when dry-spots are the damage) is the dehum.
that's my educated guess

Click to expand...

Good call although I should have mentioned pre/post dehumidifier RH values. Pre was over 70% these past two weeks, we are having record heat here as is most of the country. Post dehumidifier I'm just below 60%.

greasemonkeymann said:

was it PURE nutrients that were splashed on them? Un-diluted nutrients could do that..
if it was water that's not going to do that

Click to expand...

It was a full dose of CalMag Plus along with 1/3 does of grow big. The dehumidifier is in the room that the tent is in. Air is being sucked in from a window, the dehumidifier acts as a buffer for the room from which tent's intake ports bring it in. You had mentioned it blowing dry air on the plants so I wanted to clarify that it isn't in the actual tent.

I've exposed a shaded lower fan leaf and applied some of the water with nute drips left over in my plastic gallons. I hate to put strain on this leaf but as a software developer I'm a firm believer in "fail early fail often". Here is the leaf dry and with a few drops. I then tucked the leaf back under the shade from whence it came. Either later tonight or tomorrow morning I'll post another pic. I've also logged the highest node that these spots appear on. Hopefully I'll know for certain if action is needed here shortly. Thanks again guys.

water with the lights on could do that

water with feed in it with the lights on could damage plants leaves for sure

normally makes them look a bit rusty

I try not to get feed or water on my plants and if I do I mist them with the lights turned down and let them dry

yeah you don`t want air blowing hard directly onto the leaves and you don`t want a strong fan on them either

you just want the air to be moving so they move a bit not blowing on them unless its a very small clip type fan there normally ok

yeah dehumidifier you want blowing away from them

It`s nute burn from what you spilled on them far too much of a coincidence for it to be a deff but pretty sure you will get a cal/mag or N or PK deff before the end most people do, lol

Ok just woke up and checked and the test drops had zero effect on the leaf. I couldn't believe it but it's as if I never wet them at all. I'll snap a pic later in the morning if anything shows up but as it stands, still not sure what it is.

I've repositioned the external dehumidifier to the other side of the room in case it was caused by a concentration of dry air.

So here is the photo comparing regular leaf > leaf with nute water spilled on it > leaf after 18-ish hours. Based on these results I think its safe to say that the issue wasn't from me being careless when watering. I really wish it was, at least its something I can easily address. I had to look under a 45x glass to detect where that biggest drop at the bottom dried up and even then it was hard to see, just some laying down of what looked like tiny tiny hairs.

I did however come across another potential issue. I didn't like how my smart pots (or unamended FFOF soil) was holding water at the bottom so I placed them on wooden blocks, 2 each. This allowed air to freely travel under the pots. I moved them today and noticed this mold on some of the pieces.

Would it have been possible for this mold to travel up through the bottom of the smart pots to the roots? I've now folded up some coated metal mesh rectangles and slipped under each plant so they still have air but nothing porous. At first I had these 12" round basins but because the bottom of the pots aren't rigid and flat, it conformed to the raised parts of the basin and still held water.

Edit: I forgot to mention that it hasn't jumped to higher nodes as of yet. Currently the highest node these symptoms appear on is the 2nd.

Should I cut off the leaves that are showing symptoms? There are signs on 4 of my 6 plants on the lower nodes as mentioned but we're talking 2 leaves per plant with the exception of one that has 3 affected leaves. Would cutting them help relieve the plant of fighting whatever it is?