fighting over litter tray

Honey and Harley have started fighting over the litter tray, they both wanna sit in it and harley has been biting Honey to get her out, i had to jump in a couple of times, Anyone know any idea why this is happening or what i can do to prevent it? cheers guys

Maybe get another litter tray.
I have two buns and two litter trays, both trays are right next to one another.

If harley has then honey wants, its like when there on the floor or in the mat, wherever Harley is Honey wants to be, she always pushes him out the way, this is the first time he has stood up for himself same with food they will have a carrot each but honey will take from harley

Get a bigger litter tray? I use large under bed boxes that are big enough for two at onces.