Female cats keep fighting

Hi all

We have three cats (16 year old female, 4 year old female and 3 year old male), and recently the two female cats have been having some serious fights.

We got the 4 year old cat (Spock) when she was a kitten, and raised her together with the older cat (Popcorn). Popcorn has always been a very mean cat, but she never tried to hurt either Spock or Sinatra (the male cat), and vice versa.

About 3 days ago Spock ran across the room at randomly and started to attack Popcorn very viciously. This has happened 4 or 5 times since then, and every time Spock has been the aggressor.

She is normally a very, very nice cat and has never bitten or scratched a person before.

I tried "grounding" Spock to a room with a bowl of food and a litter box but when I let her out she goes right after Popcorn again.

What should I do?

Have Popcorn checked by vet. When cats sense illness in other cats, they tend to get aggressive towards the weaker one.

I'd take Popcorn (am assuming she's the 16 yr old) to the vet for a complete checkup.

Many times cats sense changes (bad) in another cat and will attack them. Keep them separated till you have Popcorn checked out.

The vet did tell us Popcorn would not live very long a number of years ago because of a kidney problem. While he was wrong about the length, maybe Popcorns health has worsened and we are not aware of it.

Thank you very much for your help, we'll have to discuss this within the household and I'll keep you guys up to date if you would like.