Help?! why are my white cloud minnows dying?

Ok, so ive had 4 white cloud minnows for about a week now. I know people say not to keep them with goldfish but I thought I'd give it a go, they've been fine together until I noticed this morning that one of the minnows was missing half of its face... there was a hole between his eyes where his 'jaw' should have been and hiss gills were all bloody. I moved him to a spare 2 gallon tank as a hospital tank. Unfortunately he died, the other 3 were fine. I took a look at them a couple of minutes ago and another minnows has bloody gills and is just floating near the top. I moved him to the hospital tank and added some 'disease safe' to the water. There is also a sucking loach in the main tank- the chinese algae eating type. Can you please help me to get to the bottom of why they are dying? No harsh comments please and thanks in advance