Hi FNW, sorry you are going through this 🙁
I’m guessing the fighting could have been triggered by hormonal changes post-spay. Females can drain hormones for as long as 6 weeks after spaying. Illness in one bunny can also trigger fighting. So can stress in general. The peeing changes make me think that maybe that bunny had a complication with the spay surgery or perhaps picked up a UTI. It sounds like your vet is not great but you should still ask about the peeing…Is it large puddles or kind of dribbling everywhere?
It’s also possible the peeing is that bunny being territorial and marking, which would make sense along with the fighting.
Since you are home 24/7 with them and the fighting wasn’t too bad, I think you would be OK to keeping monitoring them, and maybe do some bonding sessions with them in a neutral space. But do make the peeing is not a medical issue. Make sure to check them over for injuries very carefully. Broken skin from a bite can be hidden by fur, and means the fighting is worse than you thought.
If you have to leave them alone, you can separate them and keep them side by side. As long as they are near each other it shouldn’t disrupt their bond.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.