I've just started noticing some issues with my seedlings lately.
THE BASIC FACTS:
I'm growing various annuals and perennials (including natives) in plastic seed-starting cell trays. Soil-less medium is Schultz brand (peat + perlite). They're watered twice a day from the bottom, using a spray bottle to squirt water in the holes of each cell until they refuse to take more (this is typically 3-5 squirts).
I've only started fertilizing them the past two weeks, and I only fertilized them once each week. I use a 1/4-strength solution of Schultz All-Purpose Plant Food (NPK ratio 10-15-10). This was bottom-fed to them in a spray bottle as well.
Seedlings are kept under fluorescent lights (one warm, one cool) about 2-3 inches below the bulbs. The lights are left on about 14-15 hours a day. The bulbs are NOT hot.
Here are pictures of my problems:
This is butterfly weed. I water it just as I water my other seedlings, but these babies are developing yellowish leaves. They aren't drooping or withering, they're just ... yellow!! Is this due to too much water? Too little water? Something else?
This is pasture thistle. Besides noticing inconsistent growth (with first true leaf sometimes dwarfed, the second one giant, etc.), I've also noticed the cotyledons developing brown, withered patches. In my smallest seedling, even the true leaves are being attacked! What's going on here?? Are they too dry? But then again, if they're too moist, I'm afraid this might happen:
This is common violet. Just today I noticed the edges of two leaves suddenly looking yellow and withered.
.... the soil isn't dry! The very surface is kept dry (to prevent mold growth, which I've been struggling with almost daily) ... but underneath it's plenty moist. Is it too moist? Or are they large enough that they need to be transplanted? They don't look root-bound like some of my other seedlings (which happen to look healthier!). I don't know what to think!
Any advice would be greatly appreciated!