Ay, it's okay mama, hindi unusual yan lalo na kung nagbago lang ng formula, a few of us moms experienced the same thing when we switched milk brands, kasi ang digestive system ng babies ay kailangan ng time to adjust sa bagong formula. Since 4 days na, I'd suggest monitoring pa if may discomfort siya, pero if she seems her happy normal self, likely adjustment lang yan; pero to be safe, better check with your pedia kung matagal pa rin or if may signs of constipation like struggling or pain sa dumi niya.