I mean, I suppose it depends on your moral standpoint. I try to be objective.
On one hand, there is the possibility that the Festae is what’s keeping your jag from beating on your RTM. therefor he is currently helpful as a punching bag. But that spells out a bad ending for the Festae eventually.
On the other hand, watching the Pretty male festae get beat on till he is frail and dies of stress is rather sad for me to think about.
You can try to keep all three if you use dividers, by leaving the dividers up and slowly test out removing them ect ect. It’s really not a fun process but it can be done.
I personally recommend rehoming the Festae and keeping a close eye on the Jag and RTM I would definitely have a divider ready Incase the relationship goes south.
All three are pretty fish I wish you luck whatever way you decide to go.