hey there Posh Grow, so basically what's going on is a problem with the environment. What you're trying to do with keeping the humidity in the pots is actually detrimental to the seedlings , they dont like being over watered at all. So what you need to do is find a way to water regularly without overwatering. Try the pot lifting method to never overwater again
www.youtube.com/watch once you get more experience you'll be able to read your plant more, so dont worry. As you can see the leafs have puffy space between the veins of the leafs which is a tell tale sign of overwatering. Let the pots dry out some more and most of all remove the rocks which are causing water lockage problems as well as reflecting heat and light back on the plant leading to wilting on the bottom leafs. Hope this helps growmie ! 🚀