yeah, none of those should be kept together. awful canidates for a community tank. i would take the water dragon out and either clean his tank really well or buy him a new one. the others probably had parasites as those geckos are usually wild caught, so the dragon probably has parasites now. the people who you were watching them for must not have known anything about the animals they decided to get. it's not your fault they died, but the dude/dudett who put them all in the cage together. make sure the dragon has enough water, and they love to be misted, a lot of times when they are dehydrated they turn a darker color. i would also inspect it to see if it has any cuts or bumps. if if has cuts i would put neosporin on it with a q-tip. make sure it's water is clean, because they like to make it dirty and it is a cess-pool for parasites. what are the temps there? they like it hot, but not too much above 95F. try to cool it down by misting it or changing the bulb to a florescent. they give light and UVB, but not really any heat.
i realize this isn't your animal so not 100% your responsibility, but if you have any more questions please don't hesitate to e-mail me at otis07_@hotmail.com.
