More aggressive, all of a sudden

hey, everyone,
i have a bit of a problem. delph has been living with me since last september, and josie since last november. they didn't get along until the end of january, at which point they became really good buddies. they are still good friends, i think (they play fight by rolling around on the ground and they eat side-by-side), but it seems that delph has become more aggressive all of a sudden - she chases josie down a lot more and it seems like she is the aggressor more often than the aggressee. josie doesn't appear to like it, so i take delph away from the situation if she's cornered josie somewhere, but then josie licks herself, goes to eat, or just hangs out (meaning, she doesn't seem disturbed). this all just started happening a few weeks ago. could it be the weather? i don't want to blame it on that and have it be a serious problem by the time the colder weather comes around. i also don't want josie to be unhappy (although she gets bloody darrhea when she is unhappy, and she's had no problems with that).
i hope that someone can give me advice on what to do.
thanks,
steph

The bloody diarrhoea rings alarm bells. Distressed or not, I don't think this should be happening - although there are others more qualified than I to respond - and I'm sure they will soon.

It could be that Delph is sensing Josie is unwell and is responding how a cat normally responds - to chase away the weakling.

If I was you I'd take them both to the vet to get them checked over. Did you do that when you first got them? Have they had their innolcuations and been spayed/neutered?

thanks so much for getting back to me. yes, they have both been to the vet, last time at the end of feb when jos had a bad bout with the diarrhea. they got all the tests under the sun and the vet said it's a kind of irritable bowel, collitus (sorry about botching both of those spellings) kind of thing, and that as long as she eats and drinks well, things are ok.
they have had their shots and nothing has changed in the apartment. josie hasn't had the problem in a while, but i might make a vet appt, just in case. delph only chases her sometimes - the other times, she rubs up against her giving her kisses.

It may just be normal cat stuff. My 2 persians do really sweet stuff like rubbing up against each other, washing each other and curling up to sleep together.

Another time the boy persian will turn on the girl persian and hit her, bite her, chase her and make the most almighty moany yelling noise at her.

IF your guys are not actually drawing blood and being SERIOUSLY vicious, then maybe they're just being extra-boistrous?

Hope that helps - good luck!

Steph - does not sound too serious. They are establishing the pecking order in the house! Enjoy them.....
Deb