Blood in stool

I have two cats but I’m pretty sure it’s Hazel that’s popping blood. It only happens every once in a while, I don’t see it every day. My poor girl has suffered with diarrhea since I got her in October. I’ve tried everything. She’s been tested for parasites, been to the vet multiple times. I feed her grain free and expensive cat food. The diarrhea has definitely gotten better after a grain free diet.

Otherwise she is completely fine. She cuddles, eats, drinks, plays, runs around like a maniac. Is this cause for immediate concern? I’ve only seen blood twice and it’s been weeks apart, maybe even a month. The blood is bright red, it’s not dark at all and there’s just a little bit.