Since the other chin is new, give him a little more time to settle in. He will come around and start bathing.
Chins can get too many dust baths.. I give dust baths 2-3 times per week here.
His feed is not a food feed, any chin that comes in here on Nutriphase, Sunseed, Kaytee, etc. go to an immediate cold switch to a better feed. If you look into getting him on a better feed, you will most likely see a 'slight' weight gain from a better diet.