Dogs suddenly fighting

Question
I have 5 dogs, Zoe a female Dobie 7 yrs, Chase is a 6 yr old male yorkie/shitzu and my 3 Boston Terriers Gracie 3yrs. Max 2yrs and Buddy 8 months.  All are spayed/neutered.  My question is with Chase and Max, in the last 2 weeks all these 2 do is fight. Max is usually the one who starts the fights. They can't even be in the same room as one another.  We have had to keep one in a kennel while the other one is out and we just keep rotating who is in and out all day.  When they fight, all the other dogs will come to try to join in and help Max (except Buddy, he stays away from that) even my Dobie and she doesn't get up for much.  Do you think maybe I should take Chase in and see if maybe he is sick or something and that is why  Max is picking on him?  I ask this because when my male Dobie Jake (RIP) was sick, Chase would go after him.  They have never fought before and nothing has changed in our house. They are all walked every day and have a huge fenced in yard to play in so, they  get plenty of exercise and they all eat Eukanuba food.  We also make them all earn everything. They have to sit, shake ect.. to eat, go for walks or anything else they may want. Please advise...

Answer
It sounds as if this is a rank issue between Max and Chase.  Max has just obtained the first threshold of adult behavior (two) and is a breed that can be very dominant (toward humans as well as other dogs).  It appears that he may be challenging Chase (as Chase is the only other adult male, Buddy being a juvenile who doesn't 'count' -- yet.)  Your pack (especially your Dobe, who is the ranking female alpha) is responding to what may be a clear rank situation.  HOWEVER...your impulse to take Chase in for a full checkup (including super blood chemistry, neurological checkup and orthopedic check) is right on the mark.  If there is any underlying illness or disability (not visual), this may be the root cause.  That being said, this behavior is very much like a struggle for rank.

While you make everyone earn everything, you don't seem to have a handle on visual cues from your dogs regarding what they are thinking.  I suggest you read "Feeling outnumbered: How to Manage and Enjoy your Multi-Dog Household" by Patricia McConnell, Ph.D.  YOU are the ultimate "pack leader" and YOU are in charge here (or should be).  For males to fight on sight is NOT GOOD and you need to rehabilitate your pack situation (providing Chase checks out fine with the vet.)  If you feel unable to do this, I strongly suggest you find a credentialed animal behavior expert (NOT a dog trainer!) with a Ph.D. or DVM in Animal Behavior from a GOOD veterinary school (and with hands on experience.)  Most male to male rank problems are resolvable.  This involves the human establishing ultimate psychological rank and managing (with behavior modification and training) the relationship between the two males.  It CAN be done: I've done it successfully many times.  So don't give up hope!