Fur Loss

I adopted 2 chinchillas, Ben and Jerry, about a month ago. Ben is 4 and Jerry is 3, they have lived together the past 3 years.They have been getting along for the most part since the adoption. However, for the past couple days Jerry has been chasing Ben around during playtime and trying to hump him. This usually leads to some wrestling, never any serious fighting. Once this occurs I separate them into the top and bottom of their cage (feisty ferret). I have noticed Ben losing tufts of fur very frequently. I often find them in the cage and on myself after I play with him. After an episode of the chasing/ wrestling his fur looks as though he is priming with small patches sticking out. I think his back end is starting to look a little sparse. I am thinking the cause of all this fur loss is fur slip but it seems to occur very frequently. Is he losing the fur for another reason? Is there anything I can do to lessen the fur loss?

Ben also has had two spots of chewed fur on his flanks since adoption, these seem to be remaining about the same size.