New chinchillas fur loss

Hi my daughter has recently got 3 new chinchillas mum and 2 daughters the age of them is unknown or there back ground. The lady she got her from has had them a year and that's about as much as we know, when they arrived they were in a very small cage and fed on tesco rabbit food no hay and there sand was more like play sand than chinchilla dust that we use. My concern is the mum is small compared to the two daughters she is missing half an ear and her fur has come out in big clumps. My daughter said when she went to collect them there was a cat climbing up there cage and they had loads of animals. They seem to be doing well we have bought them a large cage changed there food and got some chinchilla dust. They come to my daughter she can now pick them up and they run round her jumping about in a pen. But I was looking at mum today her fur is really bad not to skin but looks really patchy has anyone any ideas on what could be causing this or how to try and make her better 😢