Beginning of Week 2 - Yellowing? Over/UnderFeeding?

Way too early for feeding growmie it's fine though as it should recover feed it water for a few times when it is more dryer. The best thing to do is start with like 2ml per litre the lowest on the manufacturer bottle I found after I build it up from the lowest they can handle loads after starting low and I never get any lockouts just do one feeding one watering I have done one feeding two watering and back to the feed I find they don't mind either. I can see you haven't stated if it's autoflower or photoperiod I find photoperiod ones thrive in any soil but autoflowers require alot more air through the growing medium like perlite or something. And last of all don't over water or over feed if your unsure of the moisture inside of the grow medium pop your finger slightly in the medium if it's wet it doesn't need anymore if it isn't give her some water.