Help my foster babies! Possible mange??

Hey, my name is Sam and this is my first time fostering kittens and it has been not what I expected. I started with a mom and five kittens who were only 3 days old when I got them. The mom is young herself and this is her first litter. So right now the kittens are exactly two weeks. At about one week one kitten passed away. I noticed it was “fading” I did everything I could I made sure it was warm I tried to bottle feed and it died in my hands. The next morning we woke up to another kitten who died. It was terrible! I vowed to not lose another kitten and the remaining three all seemed very happy, hungry and healthy. Four fays after the first two passed away I noticed that another kitten was fading and not gaining weight or eating. I took immediate action and brought her into the shelter so I could have an expert asses. They said there wasn’t much hope for her and to just bottle feed but not to get my hopes up. But they also noticed that her skin was strange and wrinkly. So I brought in the mama and and the other kittens so they could look at them all together. They all have wrinkly skin. The mom is missing hair on the inside of her legs which I thought was normal
For her since she was a stray. They rules out ringworm and told me it could possibly be something called mange. Then they pretty much patted me on the back gave me some antibiotics and wished me luck! Sorry this is so log now I’ll get to my question… I really really don’t want to lose another kitten. I don’t think I can handle it. I’m not sure now if these kittens are dying from fading kitten syndrome or because of this skin condition! Does anyone know a remedy for both mama and kittens? There are only two left and I wanna do everything I can to make sure they survive. Right now they are perfectly healthy besides the skin being “weird”. This is really my first time with kittens so I’m not sure what normal even is. But anyway any advice at all will be appreciated! Im a mess I just can’t lose any more kittens 🙁