Ok so there's three cats in the house but one will only show up every few days. The other two are both girls. One is ridiculously thin and I try feed her but she won't take to it. When she does try and eat the other girl will stop her from eating by attacking her. She also attacks the other cat when I cuddle her or give her treats. This same cat ALSO keeps pooing on the floor and I keep having to scrub it off the floor. The litter trays are ALWAYS clean. Please help.