Hi,

I'm hoping someone can help me - my seedlings popped their heads up around 10 days ago, and they are showing some issues, particularly one plant that has rusty spots, discoloration and wrinkled leaves. It looks worse in real life than in this pic - this one plant really doesn't look healthy. I'm concerned because I'm seeing some small pots appear on the other plants too (check the bottom left one in the first pic) and if this could be some kind of fungal/root rot issue that has a possibility of spreading then I'd rather just pull that plant.

Grow info -

5x Dinafem cheese auto xxl in 3 gallon fabric pots, germinated in the final pot with no transplanting.

Biotabs

Biobizz light mix soil with around 30% perlite added.

4x4x8" grow tent is an insulated shed (it is a typical shed, so could be mould/fungus issues lurking in there I suspect).

Lighting is a QB that pulls 480w. Had it dimmed to 200w for the first week, turned it up to 400w a couple of days ago. It's about 2 to 3 feet from the plants.

2 standing fans for ventilation and a rhino 4" exhaust fan. The standing fans have been running the whole time, but I've only just connected the exhaust fan because my temps and humidity have consistently been a reasonable range, humidity has been slightly on the high side but and I figured the higher humidity (60-70%) would do the seedlings some good.

I think I over saturated the soil early on, because I'm running a 'swick' setup, where the fabric pots sit in a tray of perlite, and the perlite tray is filled with water up to an inch below the bottom of the pots so the fabric pots can wick up water from the bottom up. I gave my fresh soil mix a good water until run off before placing in the seeds for germination, but then I put those pots straight onto the already soaked perlite. I think this may have caused the bottom of my pots to become waterlogged early one (especially as I was gently top watering occasionally because I was concerned about that top layer drying out at such an early stage). In future I will start the plants off normally for the week or two, give the roots a chance to establish, and then start them on the swick. I've removed them from the swick now as you can see, and am letting the pots dry out a bit.

I've also noticed some adult fungus gnats flitting around the grow tent, so that concerned me. I've got some Bti and have given the plants a top water with that - but when I inspect the leaves or soil with a 30x loupe I really can't see any bugs at all so I'm not sure that is even my issue, more a symptom of too high humidity and too little ventilation. Before I connected the exhaust, the whole shed did feel like one of those bug buildings at the zoo, where you walk in and the humidity and warmth hits you straight away, and now that the exhaust fan is connected it feels normal again.

I suspect the combination of high humidity and no exhaust has bred some mildew or fungus that is attacking my plants - however, I've seen a fair few pictures of calcium deficiencies that look a bit like this, as well as nutrient burn...

I'm just wondering whether I should pull this plant now and maybe spray the others down with a hydrogen peroxide solution (is there a good organic equivalent to this?), or whether it's something nutrient based that some calmag could fix (I'm in a hard water area so I didn't think this would be needed, but I could be wrong).

Thanks!