poop problems

My little one is 3 months old and gets mainly formula and a little breast milk. I just switched his formula (again) and his poops are now very thick green paste. He went twice today and the first was paste with large curds in it. The second was only about 30 mins later and was all giant curds. Should I be concerned? Picture below reference. Poop 1 on left and 2 on right. Sorry it's gross. Thanks!