I gave my daughter stage 1 foods like at 3 months.... she is 9 months now and doing great.... no food allergies and happy as ever.... she is like 28 inches tall and 20 lbs....
my doctor recommends starting with cereal at 4 months and then onto jarred food at 6 months.. there really isnt any need to give them it any sooner because the formula gives them plenty of calories.