Constipated month old

Holly

My daughter is a month old today, she's been on gerber smoothe for almost a week, I had to switch her formula because she was a extremely gassy on similac advantage. She was pooping great up till yesterday, she started pooping pebbles, I put a teaspoon of apple juice in her 4oz bottle. Is this because I just switched her formula? Or do I need to make an appt to see the ped? Any advice is great! Thank you!