Super bummed that my boys now hate each other. Let operation crate/gate and rotate for the rest of their lives commence
You might try letting tempers cool for a few days and then try it again. Jari had enough and fought back, it's not terrible and doesn't mean he hates him... it's a fairly normal response actually. But I would let them kind of mellow out for a few days before working on it more.
Payton and Auggie had a thing for a bit. Payton was the one starting it though, and Auggie was just trying to run away. But it had to do with Payton's maturity (or immaturity, however you want to look at it.) Suddenly he was a big manly jerkface who wanted to try and throw his weight around. It's possible you've got something similar, because Jari is starting to mature into a dog, and is suddenly a "threat" that must be dealt with? I think his age might have something to do with it honestly.
Basically I put Payton back under a puppy protocol... if I can't watch you and make sure you don't try to start something, you are in your crate. When he would get in Auggie's space and Auggie would throw calming signals, I would call Payton away... basically reinforcing "he gave you a calming signal so go away" to P, and reinforcing to Auggie "a calming signal will make him go away." Payton got to where I would see Auggie give a calming signal and Payton's response was to flip around and come running over to me. Maybe not the 100% appropriate response in Dog Language, he wasn't technically obeying the calming signal... he was taking the calming signal as a cue to come to me. But it accomplished what AUGGIE needed (got P out of his space) so it worked for us.
I also did a lot of working again on Payton's self-control, which is a constant battle and he was starting to get away with things that he shouldn't have been allowed to get away with. I also did things like doing some calm sits and downs while they were near each other, slowly moving them closer. Lots of rewarding for calm behavior.
It was very upsetting when it was going on and for several weeks it was very stressful around here. But eventually, I stopped counting the days we went without a fight, because it was no longer an issue. Things that were triggers for that time period... I still try to avoid having the other dogs around for... but if Auggie wanders past while I'm toweling Payton off, P no longer launches himself at him starting a fight. I don't worry about them anymore. Every now and then somebody gets a little snarky, but it's so rare and usually it's over something clear (like somebody stepped on Uncle Auggie.)
It's tough for sure. Maybe after Bubbles comes back after she's spayed you can give it another shot and see if things have started to smooth out.
I was going to work on my client's website and instead ended up playing with Payton. Payton LOVES the kneestall. Can't convince him on the footstall though. I might try doing that thing where I have him target shoes, put the shoes on my legs for the kneestall, then put them on my feet..?
Auggie also wants to do it. He has mad hops but he often overshoots LOL. So I'm laying on my back with my legs in the air and he's soaring over my legs from one side to the other. A time or two he actually hit his mark and was sitting on my legs, but he lays down immediately. It took P a while to be comfortable getting up into a sit, so maybe just more time with Augs. Boy he sure is cute though LOL.