If his eyes are sunken below their usual levels, an you haven't been misting him by hand as well as with the mistking for a few days then he is probably dehydrated. Any yellow in the Urine also points towards dehydration, as does the weakness and lethargy.Also, How old are your UVB lights? If the bulbs are over eight months to a year old, the decreas in energy could mean that he is not getting enough UVB exposure. The energy decrease could be the reason he's not showing much interest in his mistings. In which case it's time for some new bulbs.
You should extend the mistings to about two to three minutes every five hours, make sure he's getting enough of his multivitamin, and take him by a vet just to be sure! Let us know how he's doing!