Hey there! Is the feces clumped together and mushy because they’ve sat on it, or can you tell if it came out of them that way? If it’s not because they’ve sat on their poop, this can be a sign of illness, as a healthy gut should be producing healthy poops. Has the amount of poop they’re producing decreased? How are your piggies appetites - are they still eating hay, veggies, and pellets? If you’ve noticed a decrease in appetite and mushy/clumped poop, it would be a good idea to contact your vet and see what they say. In the mean time, if you have determined that the poops aren’t from them smushing them, supplement your guinea pigs with critical care, as this will help eventually return their gut to normal. Also, if the poop is more of a diarrhea/not fully formed, I would recommend removing pellets and veggies from their diet and only providing hay and critical care for the time being!