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Coccidiosis can cause bloody poops, but it is rare for chicks that young to get it. Is it reddish-brown liquidy poop? And are they having normal poops in addition to the red-brown liquidy stuff? If so, you may just be seeing what is called "cecal" poop. I believe that they do this stuff about 1 in 7 or 8 poops, it's normal.
If that (cecal poop) doesn't explain it, there may be something else going on. There is a chance for various intestinal ailments that can cause bloody poo. But at 1 week old, I'd pretty much rule out cocci.