So this morning when I went and checked on Si there was a lot of darker poop spread around his area, and his litter box had some dark poop. There was also some smudges on the ground and his litter tray where he has obviously gotten it stuck on his foot and bum. I hated to do it because we are still so new to each other but I picked him up so I could check his bum and he has poop smeared onto his genital areas, it seems mostly formed just softer/sticker than his normal poops.
I noticed the last two days that he went from eating LOTS of hay and barely any pellets, to eating pretty much all pellets and no hay (even refreshed his hay, tried hand feeding it, putting it out of the litter box). He was still eating and drinking so didnt stress.
Here is a pic of the litter tray you can see the colour difference

Is this something to worry about? Or just because of the excess protein from the pellets with no hay? Any tricks on how to get him to eat his hay again?
Also I need to clean his bum
, which sucks because I feel like he is going to go back to not interacting with me now. Any advice on best way to clean him up?