I agree, test the water, and then please post the results.
Is there a predator that could be attacking the fish - for the torn fins and blood? Turtle, heron, raccoon?
Is there some way you can rig up a filter? Clean water is important to fish health, especially as they grow and put more stress on their environment (meaning, more fish poop, amonia, nitrates, etc.)
Is it possible to do a full or partial water change?