Tufts

I have 4 chinchillas, I bought them over the summer about a month or two apart... the three Zen, Dartagnan and Storm are all in one critter nation cage and the other Clementine is is a separate cage I just got him a week ago and as of right now he isn't getting along with any of my other chinchillas except when I put them all in a playpen they do just fine. So onto my question, over the last month I would say I noticed fur tufts in all 3 of my chinchillas. Lately Storm has been making a new squealing type noise... I've heard him make this noise before like when he is sleeping but now it's louder and more often. Dartagnan is very talkative and he's always making his cheerful chirp especially before he chases Storm or Zen and he rapidly wags his tail in a circle. At night I hear them chasing each other around the cage Zen and Storm will bark at Dartagnan since he does most of the chasing ... and I've been seeing zen storm and Dartagnan get on their back legs and bark at Dartagnan....but they groom each other they cuddle and they hump each other which are all good signs but I don't understand what the fur tufts are all about? Could they be stressed out all of a sudden? Is Dartagnan in heat? Should I separate them? There doesn't seem to be any injury or anything like that just the barking and fur tufts...
They are all boys.