If the cat is in a good mental state except for soft stool, then adjust the stomach first and feed a little probiotics every day. Kittens under three months are fed a quarter at a time, and kittens over three months are fed a third at a time. It can be mixed with cat food or water. After the cat eats cat food, it can stop.
You can't be too anxious to change the Champions League cat food. Generally, the food replacement cycle is about ten days. If it is too sudden, it will make the cat a little uncomfortable with the taste of the new food, upset the stomach, and then soften.