Have you tried giving them floor time too? I used to give Harvey time out when Artie was ill, and Harvey took advantage of this, I put Artie and Harvey in their indoor run and used garden mesh to sperate the two but they could still see each other, and left them for fifteen minutes for floor time and rest time!
In that time I cleaned down their hutch and put fresh bedding down (lots and lots of hay), in that time Harvey would cool off and i'd put them back into the hutch. I'd really recommend lots of hay, and to scatter the food around veggies and pellets so they have to forage for it, this keeps their minds occupied in finding the food and not squabbling over a pile of it
If you can cardboard boxs are good, two entrances in each hidey so one cant get bullied into a corner, and it's a safe haven for him to get some peace too. Cardboard boxes also keep piggies amused!
You could also try bathing both of them, and steralising the cage top to bottom and rearranging their furniture so everythings new and exciting, they'll be too busy exploring to start arguing!
Good luck hope they resolve their differences soon
Forgot to add, when I took poorly Artie out for cuddle time I'd feed him porriage oats and extra veggies to keep his weight up