I see in the picture you have a gas inlet valve for a hot water heater or something. Carbon dioxide is heavier than air. Just the carbon dioxide release from the pilot light may have been enough to kill your plant. I'm betting its sick from loss of oxygen. Move your plant away from carbon dioxide,give it lots of oxygen with help from a fan and water sparingly and get a spray bottle of clean water and spray it a couple times a day. It looks pretty bad but it might come back. I think I would also put it back into veg cycle 18/6.

Also get that gas line checked to make sure you don't have a gas leak.Natural gas is heavier than air too so could have been the problem.