What can I do about my cats and their territorial fighting?

My two adult male cats are being very territorial for the last few months. There has been a lot of bickering and noise making and pooping next to the litter box/not covering type behavior. I’m not sure why, they have lived together for 7 years and always got along fine up until about 6 months ago, give or take. One of them was treated for a UTI a few months back, which I thought might be behind the litterbox behavior, and perhaps stressing him out, but nothing has changed although he is healthy now.
Normally when they are physically getting into it, I just shoo them apart.
The real problem is that in the last few days I notice that they are taking turns peeing in the corner of my living room. Not okay. I’m also getting new carpet next week and so this needs to be dealt with ASAP.

I’ve had cats all of my life, and usually I know how to handle things, but I don’t really know what to do about this. Any ideas? :(