Was using inverted white lamps as a on/off switch for my cursed earth mob farm but after much trial and error I found that the lights (tho not emitting light and F7 confirmed that) were acting like they were in respect to not allowing mobs to spawn. not completely however every few mins a mob or 2 would spawn.

I know lamps do not allow mobs to spawn on them, but that should not effect the surrounding area I think.
Do you have lamps on the ground which could be preventing mob spawns (regardless of on/off state)?

No, they were in the ceiling. after removing the lamps everything went fine. it does seem weird to me though

Don't know, but can't see why it would effect mobs if they were on the ceiling. Most likely something else here causing the issue,