what should i do?

Hi my young adult rat is having diarrhea for last three days but other than that she’s doing fine, she’s active and acting as usual. 2 weeks ago i changed their food but everything seemed fine. Also other rats in the cage are completely fine. When she started having diarrhea i change their food to just dry food no weggies. Im not sure what to do, wet in my area is pretty expensive but if she’s really sick i’ll take her. what should i do