Due to a lot of issues early in the process due to...

hard to tell color under lights, but if i recall these look perkier already eh? Seem to be growing well right now. So, i think you are on track! :) adjust lights based on the internodal spacing you observe... keep them tight, but not on top of each other and you'll grow it at a quick speed. so, try to observe the growth each day... the moment it slows, begin your fertilizing cycle. watch for hints... if it gets dark, that's likely too much fertilizing (maybe 2 water-only irrigations between or 3 etc all depends).. simply adjust. If it fades or slows down, up your fertilizing frequency. keep a consistent ratio and concentration when you do feed (possibly per strain)... if those above solutions don't fix anything, you likely need a little less or more in your mix when you apply it. trial and error... but, be somewhat smart about it over time.. don't have to be crazy, but a note here and there helps a lot over months or years of time. This is never-ending... but, you'll likely minimize it to the point it only happens with new and possibly sensitive strains in short order. feels overwhelming at first.