Rashes at private parts. For rashes?

Hello Experts, My 6 months old daughter got rashes at private parts and also suffering from motions (5 times a day). The problem is since last 4 days. As per doctors advise we used bifilac 2 times a day, siloderm cream for rashes. Actually we have changed the milk powder from similac advance stage 1 to similac advance IQ+ stage 2 15 days back. Does it creates any impact in health conditions ? Does siloderm works effectively for rashes ? As there is no result for more than 3 days after using siloderm and bifilac, we visited the same doctor again for suggestion. (We avoided using diapers from last 4 days and  Regualarly washing nappies with hot water). Now doctor has entirely changed the prescription and asked us to use T-bact cream 3 times a day, monocef syrup 2times a day for 5 days, zinc drops for 14 days and also changed the milk powder to Isomil or Nan low lac and enterogermina to avoid motions in place of bifilac. We are very much worried as we see slight bulge at her private part