100% it's thick milk so it clogs them up! Amelias is also on lactulose which helps it unclog definitely advice you to try that the docs will percribe you it :). Sometimes it clogs up loads that it'll end up hurting there bums so I put vasaline in in and around the bum which helps it slide out :) Xx
If your little one was constipated then it's normals even if he was struggling to go, try giving your baby a bit of cooled boiled water worked wonders for my little girl x
I'm not sure with ur son being formula fed if his poo is supposed to look like that, I would google it and maybe take him to a walk in for them to look at. Did ur son have any jaundice when born? X
My daughter is two weeks old and the health visitor came yesterday and mentioned that if her poo becomes hard and pale take her to the docs. I know camera lighting may be different but I don't think that looks normal in my opinion but U can google it. Is your child breast or formula fed? X