The new information (the grey spots) sound like a fungus. Here's link for you on common diseases, and treatments. Please look through them, and see if he's exhibiting any other symptoms. Otherwise, my diagnosis (without seeing the fish), is a fungus. Treatments can be the ones listed or PimaFix. Please keep me posted on how things are going and what you're using.
Best of luck.
Diagnostic chart
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Phishie
"An ounce of prevention is worth a pound of cure."

