This is long, so I apologize...
Today I finally got my check and headed to Petco to get everything needed for my first sorority. A shiny new 15 gallon, heater, filter, live plants, hiding places, gravel, the works. I also picked up 4 new girls, in addition to the 2 I had at home.
So I got everything set up, and eventually put the girls in. Awesome, right? No. ALL of them, besides my little CT female who was probably too scared, began to fight within 5 minutes of being in the tank, and none of them were backing down. It just got worse and they actually began damaging each other's fins, so I took them out and now each of them is in a seperate salt bath, and my CT is alone in the tank.
So, here I am. This is what I feared would happen, and of course it did.

What did I do wrong? The only thing I can think of is that I bought females of similar sizes..But I thought that's what you were supposed to do? I bought a female a while back who was larger than most females, and I liked that because she looked happy and robust so I bought other females matching her size. Are they more aggressive or something because they're bigger..?
If someone could give me advice, I'd really appreciate it because I feel like giving up on this idea of having a happy sorority like everyone else does.