Your instincts serve you well, the soil was too hot for early growth. I dunno if I'd take drastic steps to try to fix it at this point unless it gets worse. They're getting old enough to handle it soon enough. The optimal pH in soil is 6-7, so while it's on the high side it's perfectly OK. Really soil is pretty forgiving to pH imbalances as long as you're not waaaaay out of range. Many soil growers don't even measure pH, lol. While VPD is a great tool for optimizing growth, really all low humidity means is it's gonna drink more unless you lower temps to compensate-it's not causing this. Speaking of drinking more, once you're beyond the seedling stage, don't "just water the outside" lol. Water fully and wait until your pots are light until watering again.
I swear I think people would be better off just asking AI than some of the answers that get thrown around on here...