My cat is depressed, what do i do? PLEASE HELP

I have 3 cats, Cookie (the oldest), Baby Kitty(middle), and Ktten(youngest) and dont hang me out to dry on the names, not my idea.
But anyway, we recently we had to give away Kitten. Cookie and Kitten were the best of pals, but she urinated all over the house, and we tried everything, but we gave her to a humane society. But lately Cookie who has been acting agressivly, moping around, and he is what they call a "mute cat" his meows are kind of empty and dont have sound. But he has been really loud latley and not acting like him.
I've done alot of research, and these are tell-tale signs of "cat depression" I want to know if getting another cat would help the situation or what I can do to help, if someone can respond soon that would really help!
Kitten is now up for adoption.
http://www.animalhumanesociety.org/a...etail/19897990

Oh, how sad! Hopefully Kitty will find an owner who will be able to figure out what her litterbox issues were. She may just want to be an "only cat" which of course was not possible at your house.

I would not add another cat at this point. How long had it been since Kitty went to the Humane Society? Is do Cookie and Baby Kitty get along? Is Cookie eating and pooping normally? How old is he? From the sound of it, there may be something medical going on - pain will often cause aggression. A vet trip is in order, and then if you get the all clear on his health, we can help you with him emotionally!

We brought Kiten in on the 26th of May, Baby Kitty usually get along, but Baby Kitty is a scardy cat and Cookie has been acting agressivly towards Baby Kitty. His eating and pooping habits have been regular, and he is 6 years old, and we can try to get him in within the next 2 weeks.
But my mom wants another cat soon, but shes not sure when the right time will be, and Kitten peed all over my room, so we are pulling up the carpet and washing the tile underneath before we get another cat, so im debating on when to get another.

Make sure you clean the wood, once you remove the old carpet, with an enzymatic cleaner, so the stuff we humans cannot smell that mark a spot as "good spot to pee" will be removed.

Try playing a lot with Cookie - fishing pole-type toys so he can practice hunting, and other games he likes, to get him tired out. You may even want to try taking him on walks using a leash and harness, anything that will tire him out. Give him things to hunt that are NOT Baby Kitty. And maybe your mother, instead of adopting a new cat, can concentrate on building up Baby Kitty's confidence, so she will not act so much like prey, and won;t tempt Cookie to attack her. I would certainly not add another cat into the mix before getting the situation with these two figured out!

Alright, thank you! Play time will happen very soon!

Very good, and do keep us posted!