Hi There. I Just Started My 1yr Old On 3.8%

Hi there. I just started my 1yr old on 3.8% organic cows milk. On Dec 8. And noticed her stool is more frequent. But now it has tons of kidney beans objects. In her stool and she has a rash in body. And her whole diaper area is all puffy and red. Severe diaper rash. Need help.