I have at times over the years had up to 20 individuals living together quite harmoniously in one enclosure without injuries to any. However the difference between my situation and your own is that I did not have so many related chips in with each other. I used to swap the babies with other breeders every spring and the colony was built up over 4 years to the maximum number. Nowadays I don't have as mush space and only keep a maximum of 6 in my aviary which is 15ft x 6ft x 6 ft and have no problems with any of them.
My thoughts are that perhaps(and I am no better at reading chipmunk thoughts than any other)being related they have now become pissed off with living in each others pockets. This could be down to a feeling that the gene pool is too small or simply that they would prefer just to meet at weddings and funerals like a lot of human families.
When you look at all the factors which could start a fight for dominance which is after all survival of the species it is the hardiest and biggest who generally get to mate and produce offspring you appear to have quite a lot of jealousy going on (to put it in human terms) which is now turning into bullying.
As for "Why now" My suggestion would be that they can foresee a very harsh winter coming and despite out human efforts to supply enough food and shelter for all they do not see it that way all they see in their siblings/parents grandparents even is competition, they are not brothers and sisters any-more than you or I are related in their minds, they are individuals whose main priority is number one.
Many will come play with you and allow you to touch stroke or even carry them, this is fine but they are still playing the dominance game with you, they see a source of food so overcome their natural fear of another species in order to survive, those who are not so willing to come to you will be green with envy in human terms that they can not overcome their fears as well as the others and will resort to bully tactics to get what they want.
I know how much you love and care for each and every one of your babies but my only suggestion would be that you have a decisive turnover of individuals; if not now; then definitely in the spring before they begin breeding.
We all of us at time tend to make the mistake of thinking of pets are Humans with Human emotions and aspirations I don't know anyone who does not tell their pet dog or cat to ask mummy/daddy for a treat/walk but we must remember with smaller pets that they are wild animals and have primal instincts of survival which are far more ingrained than our own. They will fight and kill others to ensure their own survival no matter what we try to do there is no real way of reassuring them that everything will be fine during the next few months when their instincts are saying you must save/hoard/eat all the food available; regardless of how much there is you must have it all.
THESE are just my own psycho babble thoughts on the workings of a chipmunks brain I am sorry I am unable to say with any certainty that the squabbling will pass, or that by pairing "A" with"E" rather than "B" the situation would resolve itself.
It must ultimately be your decision as to how you resolve things but personally as much as I love each of my babies for their individual personality and charm should one or more decide they wanted their freedom from the group situation they are in I would swap/trade/sell them to another breeder/owner/carer rather than keep pandering to their demands for extra space.
I hope you are not offended by any of my thoughts but I only ever think about the welfare of the chipmunks in my care. Sometimes to the detriment of my own human family
I do hope though that things settle down at least for the winter. and each of your chips can go forward from this bad week.
