Advice??

Hello everyone! Im desperate for your advice
These two bunbuns are Nanachi female 6.5 years old (grey) and Chidaruma male 4.5 years old (red) both neutered. We had them both since they were 3 months each, one after another, first Nanaci, then Chi. They have same mommy, just born 2 years apart. On their first encounter, when Chi was tiny little pumpkin, Nanachi first kissed him through the cage, but then bit him on his nose😭 Ever since we tried to bond them by the book a few times, but they eventually just end up fighting. They can only tolerate each other in the same carrier to the Vet, they even kiss and comfort each other there????
We gave up our hopes to bond them, so we separated their playpens and now they walk by the schedule only, one after another. These mfrs even sleep next to each other's pens!

But my problem is not that they fight, but that they last week started peeing everything everywhere all over the place, they have this piss fight once a year, they even drink more to produce more urine! They just cant stop marking the territory 🥲 what should I do? My whole small apartment is soaking with their urine welp 🥹Please help