My Twinkie has diarrhea? :(

I've noticed the last few days that my cat's stool has changed. She's never had this problem before. Her stools have always been in "tootsie rolls" shape and solid. Now I noticed that they're mushy and more like a "pancake" shape. I noticed that when she goes it js a bit runny but still a normal light brownish color.

The only thing that has changed is her food. It's the same brand, just a different recipe. We used to give her Hills Ideal Balance Chicken and Turkey. But they didn't have it so this time we got the Chicken and Brown Rice recipe. Could the change be causing this issue and should I be concerned? She's still active and fulll of energy. Only thing that has changed is her stool.

Also adding, I do plan on taking her to the vet during the week. But just wanted a heads up of what could be causing this

If it'd dry food, that's very possibly the culprit.  Dry food changes need to be gradual over a period of 10-14 days to prevent tummy upset and bowel problems.

It could be too rich for her, it might be good if you can buy a bag of her old food or get her on canned, I find most kitties do really well on canned food, settles their tummy, try to stay away from any with gravy/sauce though.