You mentioned Iguana at .5 ml/ cup.........
That's got me puzzled, you didn't pour that straight into the soil, did you?
I've never used it, but I would think whatever quantity the instructions say should be diluted to a gallon of water.
They should be old enough to start feeding, I usually start feeding between 21-30 days from sprout.
I know you mentioned temp of 74, but is that at leaf level, or room temp?
Do you have a fan blowing across them to move the warm air from the bulbs and strengthen the stem??