I bought these 3 lemon meringue seedlings in early Aug and potted them about 2 weeks after I bought them. They have been in these pots for over 6 weeks and the leaves have been wilting for the past week or so. The weather here in Phoenix has dropped but we are still having 100 degree highs and I have not changed anything. I wanted to see if anyone knows why the leaves would be wilting like this as they look healthy otherwise. The leaves are crisping up on one of them. Thanks in advance.
Your soil-mix looks like almost entirely peat moss or something similar, way too much moisture-retention for mango roots. They like quick-draining, sandy soil; wet roots for long leads to root rot. I'm guessing the roots are already wasted and they'll all die no matter what you do now; it's going to stress them to repot and they are already super-stressed. Might as well try though, get a bag of cactus soil or other quick-draining, dry medium. I'd remove all but the single healthiest leaf from each, and cut that single leaf in half (or more), width-wise. Those leaves are doing more harm than good, at this point, but you don't want the plant without the ability to resume photosynthesis if it does recover.
I killed many, many seedlings when I started; getting the soil right is the biggest challenge and mango seedlings will fool you. They'll look healthy and great for quite awhile in just about any potting soil mix, pushing growth and pulling all their needs from the seed. When the seed energy runs out and they have to rely on their roots, they can die in what seems like days.
