I use to have problems with Ivy and Holly they are sisters and standard grays. Then I picked up one Holly will keep one ear down most of the time, and Crysta informed me that Holly has a more curled up tail then Ivy. You just have to look for the little things.
It gets better! I Promise!
Some chinchillas will even chew their fur when they feel board. Make sure you keep plenty of toys for him to chew on in the cage.
I have a girl Ivy when shes stressed or board she will chew. So I try to mix up their cage when I can. I notice she will chew less when she has more to do...