Personally, I'd guess temperatures, but CFLs will lose lumens over time. 6 grows using the same lights throughout veg and flower? if so then

veg @ 36 days x 24 hours = 864 hours x 6 veg periods = 5184 hours
bloom @ 60 days x 12 hours = 720 x 6 blooms = 4320 hours

Add in some wear and tear for turning them on and off and you're at about 10,000 hours on those cfls - getting pretty old. I would imagine the output is significantly less than when they were new. Get a new bulb and compare them side by side. Or just get all new bulbs and rule that factor out - they are cheap and the ones you have seem to have done plenty enough to be "retired" or used as spares
Tokudai Reviewed by Tokudai on . CFLs going bad? ok so iv had the same 6 cfl for my last 5 grows and for the first 3 they were fine but in the last 2 the plants look real limp and not good, but both of these were from the same bag of some fire fire fire kind bud. i know its not over watering b/c i let the media dry out b4 i watered again. and i noticed that for every grow since the first the plants have taken longer and longer to grow and finish. so my question is does it seem like its the lights going bad or the seeds or the enviroment. ill Rating: 5