She seems a lighter shade of green compared to the...

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.

Hey I saw you mentioned slow growth, I read that those xxl strains are often slower growers/maturing. Anyways the seedling will pull out of it slump as long as you're giving it basic love, good hours of sunshine, a warm humid environment (perhaps a plastic cup over the top to keep it high.) Good watering and drying, and easy does it on those nutes. Cant wait to see the rest of the diary details. Happy healthy growing.

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.

Hi there! I'm thinking about overwatering: your soil looks very wet, such young babies don't need big amount of water, your soil needs to alternate between dry-cycle and wet-cycle. I'll be around, good luck with this baby!

Don't worry, everything looks fine. Although I would stop all feeding, you might burn them