I have 2 indoor cats that we have had together for about 8 years now. They have never totally got on together but tolerated each other. But recently they have started fighting all the time and the older one has started spraying on the front door on a daily basis. I have tried everything I can think of and hope somebody has some other ideas- I have taken her to the vet for a check up which was all fine, we have Feliway around the house and we have 3 litter trays. We also make sure they are fed separately and we have lots of cat trees and beds around the house so they can easily have their own space. Any ideas on what I can try next? Thank you!