Okay to mix finch species in cage?

Do you buy your finches around the warmer seasons? I had finches die on me too, and i found out it was because of the weather that i was exposing them to, which was the colder seasons. As for mixing different finch species i'm thinking its ok. That's my opinion though so don't try it unless your comfortable with it. I don't have cordon bleu finches in my house; I'm taking care of Zebra Finches.