Growth halted at the cotyledon stage
A variety of seeds I planted in six flats - dianthus, cortaderia, thyme, Edelweiss, annual cut flower mix - all germinated speedily (within four days). Now they're about an inch high and for the past four days there has been no sign of true leaves starting. The same thing happened last year and the seedlings ending up dying. (I never had trouble starting seeds before that). The only difference is that last year I made my own soilless mix, while this year I used ProMix hoping to not repeat last year's disaster. I'm using 40w bulbs 2" above the trays. Sterilized trays and pots with bleach water. Room temp is 64-68'F. Fans are on. No damping off.
Any ideas? The only logical explanation I can come up with is that I am cursed.