She seems a lighter shade of green compared to the others on the exact same feeding schedule and in the same soil mix. Using tap water that has been been sitting for well over 24hr. Is this a PH lockout I’m experiencing or do you think it’s a deficiency?
Get some heat into that media. She looks cold-stunted to me. Air temp is important but for young plants, media temp is more important I've found. 22c media temp min for young plants, 28-32c and they thrive. HTH
If you balance your water to arround 6ph i wouldnt say its a ph problem.
For a seedling she looks very much ok .
My seedlings dont get any nutes until week 2 or 3 of veg and its the same.
I would say stop nutes for a week and dont worry.
I'd say they look fine, nothing to worry about so early on. Night temperature is a bit cool and may cause stunted growth. You can use anything that will give a greenhouse effect to bring up the temps over night. Also, at this stage and up until around 4 weeks, you don't need to be feeding your plants any nutrients, this can also stunt them giving them too much, too soon. Your growing medium has the sufficient amount of nutrients in it already, so feeding it so young could end up being overfed and then nutrient burn, root lockout etc. So only feed when it tells you too, with early deficiency signs and this is way to early to tell. Hope this helps.