Hello

Question
I live in Texas, and I purchased a total of 3 finch birds last year from a fair. However, 2 of the 3 birds passed away shortly. This past March since there was only 1 bird remaining, I decided to purchase 2 more finches (Zebra. Tonight when I was getting ready to bring them inside, I noticed 1 of the male birds was laying on his stomach. I immediately took him out of the cage, hoping that he would still be a live, but he had already passed. I would like to know what is killing my birds? I changed their water and food everyday. I've spent $50 on finches alone, and I'm afraid to get anymore because it seems the same thing is going to happen again.  

Answer
Unfortunately, there isn't enough information you've given me to tell you what could be killing them.
What food do you give them? Where do you buy it?
Do they click while they breath?
Do they have "sleepy eyes"?
Do they spend time on the bottom of the cage?
How often did you clean their dishes and changed the bottom of their cage?
Where did you buy the birds? What were the condition of the other birds in the store?
Any information at all will help me narrow down a possible cause. However, an autopsy might also be needed. Any avian vet should be able to autopsy a bird.