Cat chasing in small space! Help :(

[Bugmom11]

I live in a studio apartment with two female cats (ages 1.5 & 5) and when I’m not in the apartment, they get along fine. During the day if I’m home, they only compete when they are hungry. But all of a sudden between 12am and 1am if I’m home, they start to chase each other to the point of some scary yowels. I can only assume it’s jealousy-triggered. My question is, how do I mitigate the fighting if i can only separate them between a cold bathroom and the huge main room (that has me in it)? Would separating them like that only make things worse? Any herbal remedies to calm newly competitive kitties?

[Mollycat]

How do you know they get along fine when you're not there? And do you mean 12-1 in the day or in the night?

Are you sure the chasing is fighting and not rough play?