This is a test of the Philips 3k and 4k cmh bulbs in flower. I'll need your input as well comparing pics. I should be able to match week for week. All done with same strains, same room placement, same temps/rh. I will need to lower co2 from 1200 back to 1000. Lessen the variables. Bulbs being tested Philips master Greenpower elite agro t12 930 (3k) Philips master color cdm elite t9 940 (4k) 1 brand new bulb far left (#1) hood. All other bulbs have maybe 1200hrs tops. Fixed hoods, I use cinder blocks, milk crates, or tubs to raise plants between 36-48" tops. 1 thing I did notice, (may be due to the winter weather, cold basement) my a.c. doesn't need to run as often as my co2 is lasting much longer. I'm betting the 4k isn't as hot as the 3k bulb. Here's a link to a past cmh grow.but with the 930 (3k) flower bulb. https://www.thcfarmer.com/community/threads/demons-4x315cmh-v2-0.86733/ I'l try and get some pics later. Flipped 11/2 to 12/12 I'l take these to 64+ days. I tossed in a cannatonic4 cbd last night. My patients will be needing her soon.