I changed my 7 week olds formula from SMA gold to Aptimal Comfort for colic and constipation a couple of weeks ago due to BAD WIND, and his poo's have been runny and green since the change but for the last two days it's been stringy! really watery, yellow and bitty.. and he's does them about every hour not huge ones but everytime i open his nappy theres some and you can here him fart them out is this normal??