Bloody Spots On My Guppy

One of my guppies has some bloody spots on her body, I found that when I came home yesterday and it was a few spots but today is already all over her body. It looks like she got beaten up but I don't see any other fish attacks her. I have 7 guppies, 6 zebra danios, 4 cory, 3 algae eaters and 2 silver dollar. Anyone knows what is wrong with her?

How long has the tank been setup? Is it cycled? How big is the tank and what are your water parameters?

I have the tank for about 15 years already, I used to have red parrot fish and silver dollar but most of the died in the last few years and only two silver dollars left then I recent bought the other fishes. The tank is 45 gallon and regarding to water parameter only thing I know is the temperature is at 82F, I know they should be in lower temperature water but my place is always hot and 82F is the lowest I can give them. I don't have any thing to test the water so I have no other info about the water.
I just fed them and then I walked away, now I got another badly injured male... I put them both on a 2.5 gallon tank right now, the female seems ok but the male looks dying already. I don't know is killing them.

The male died this morning when I got up, there was no visible damage on the body. I think he might be hit by the silver dollar when they were going after a flake or something. The female still alive but not looking good, she is like having internal bleeding.
By the way, can someone tell me what do I need to get to test water quality?