Hi! i got two guinea pigs back in February and i recently i noticed one of my piggies’ back foot is starting to turn greyish. shes about 10 months old and has all pink feet but the bottom of her toes on her back foot are starting to turn almost a grey colour. at first i thought maybe she stepped in poop so it wiped her feet with a wet paper towel but nothing came off. as i looked closer at her foot it looks normal besides the colour change; no scabs or sores and she let me touch her foot and it didnt seem to hurt her at all. is it normal for pigmentation change to happen on the bottom of their feet or is this something i should be concerned about? I'm still pretty new to owning guinea pigs so i want to be sure its nothing serious