The lid is stock and contains the stock bulbs in as well... not MH. It does contain a heater in the tank but should not be on during high temperature operation, but will unplug just to be sure.

Also would to the first response, the chiller is only 6 months old and if it needed refrigerant, would it chill at all in the first place... why would it keep getting colder?

Thanks for all of your suggestions so far.