Slightly OT red eared terrapins

Hello, I’m sorry to post about red eared terrapins, but you are the only active terrapin-based group I could find. I need some advice. My boyfriend has two red-eared terrapins he rescued when they were nearly dumped. He put loads of effort into finding out what they needed and they are all set up with heat pad, scenary, proper lighting etc. We take them for regular check-ups and they have been growing since in his care. This weekend, they distended. The soft skin around their legs and throat bloated out and their skin seems to be floating off in small flakes (only noticible when they are in the water). I have a vet appointment later today but any advice or thoughts before then (to make me feel like I’m doing something useful for them) would be very very appreciated. I want them to be okay, the partner is so attached to them and has put so much effort into making them happy and healthy. Thank you, Felicity