It's my first time starting eggplant seeds indoors. The first true leaves, though large, are starting to turn yellow. The 2nd to 4th sets of leaves are still dark green. The plants are about 4-5 inches and not leggy at all. Do I need to fertilize these young plants at all before it's time to harden them off?
The yellowing sounds like they need nitrogen, so yes they are tall enough to feritlize. Do the new green leaves turn yellow as well as they grow? If so then yes they need nitrogen. Still it does not hurt to fertilize them, all plants need to be fertilized or you can also mix some manure in with the soil. Do you plan to keep them in a pot as well?