So, first I would back off on the feeding. Not sure what fish you have, but unless you have fish that require multiple feedings, most do not require daily feeding.
Next, I would vacuum your rock during a water change.
Finally, Are you using the WP-40? How long has it been since you cleaned them? They lose circulation power if not cleaned on a good schedule.
Not knowing your too much about your clean crew, it sounds like part of the food and detritus is falling onto the rock which is feeding the cyano and algae. I'm not to keen on the use of Chemi Clean...it may solve in the problem short-term, but the problem still exists.