My daughter is 2.7 years old. She has been potty trained since she was…

My daughter is 2.7 years old. She has been potty trained since she was 2 years old. There have been no accidents on the potty. For the last four days, she has been having diarrhea in her underwear and then running to the potty every time. I thought it might be diaper rash or an infection, so we did a urine analysis. It's perfect. What could be the problem? The pediatrician suggested neurology, as we recently had another baby girl. She says that this could be the cause. Also, because of her frequent tantrums, all gadgets (phone, tablet) were removed. Only cartoons are allowed on TV. She prescribed POntagam for her to drink. Should I give it