Has Hodges been to a vet since the attack? I'd first have have him evaluated by a vet and also have them check his sight and hearing. He's a senior dog and could easily be having aches and pains due to old age, and if he's also going deaf or blind he may have reacted to their aggressive play in a way that spurred a reaction.
(I would bet money that it's the shar-pei mix that is the most aggressive.)

How long have you had the 2 younger dogs?
I would keep them away from Hodges for now and if they haven't had any training I'd start them both (separately) in basic obedience training.
At this point it is not safe to ever leave Hodges alone with the other 2.

Hodges may have simply started the situation by reacting the way a 13 year old dog may act towards fiesty pups---like a grumpy old person. And the pups ---reacting on survival instinct---fought. So, it could have been Hodges that caused the fight---by a bad reaction.

I agree Hodges should never be left unsupervised with the pups.

You should be able to train the pups to avoid Hodges---which would solve the problem---but only under supervision. Once they get older---three or so, they should not be as uninhibited around older dogs.

So all three are males? Fixed?

How long ago was the third dog added?

Sounds like they are working out who is alpha dog. How much socialization has Leo had with other dogs?