Hello everyone I've been feeding my little one Nestle Nestogen 1 formu…

Hello everyone I've been feeding my little one Nestle Nestogen 1 formula for the past two days, and switched to 2-cup last night and she started having diaper rash. Could it be from the formula? Usually I breastfeed but at night and if we go somewhere, I give her formula, everything was fine with the first one, but now I gave her 2-cup at night and woke up with diaper rash, as it was yesterday and today. What should I do? Change the formula or can she still drink 1?