36W PL should not be an issue so I think we can safely rule lights out.
If its not feeding, that makes things a little trickier and we may want to look deeper into the causes. Doing water changes may help improve the situation.
If the cause is bacterial infection - The bacteria could have been present in the tank all along. It could have struck when the lionfish's immune system got suppressed.
FW disease are likely to not affect SW fish but its possible to have a SW version of the disease. This is much like how whitespot occurs in FW & SW aquaria but caused by two different parasites.
Its possible it may have been brought on by flukes. Check out these references:
Fish eye disease
Flukes
Here's a closeup of what I believe is a goby with eye flukes:
Close-up of fish eye with flukes