I have 2 male cats, one 7 one 3 years old, the 7 yr old has been neutered, the 3 yr old has not. both have their claws, and are strickly indoors cats. both have their claws. both have lived in the same house since they were kittens. & both have gotten along great, UNTIL YESTERDAY, all of a sudden, they start growling & hissing & attacking at each other, and haven't stoped. How come all of a sudden this is happening? it is getting annoying, they fight all night & keep the whole house up. I'm worried, Is something wrong? what can I do?