I Changed My Grandsons Nan Formula To Nido 1+..ftom Last

I changed my grandsons nan formula to nido 1+..ftom last week friday on saturday he picked up a fever n runny nose den he became heavily congested n by Wednesday he picked up a chest infection as per docs visit...he is on meds but da chest is quite heavy. .plse advise if it had anything to do with da change in his formula