8 month old baby have rashes. Be done?

Hello Doctor, My 8 month old baby developed some rashes around her diaper area and also hands and fingers. I fed her tomato puree( boiled and mashed tomato cooked with a little butter) on 10th, tomato and spinach puree on 11th and 12th, on 13th she didn't try any new food but I gave her some outside phirni (1tsp) which I totally regret now and we changed her formula from farex stage 2 to nan pro stage 2 due to unavailability of farex. On 14th she passed loose stool once and had some rash and today I.e on 15th rash on hand increased a little. On 14th and 15th I haven't fed her any new food. She isn't having any itching or any discomfort due to the rash and seems perfectly happy. What should be done? Please help