Plants use co2 for assimilation in its all growing stages. Normal air co2 levels in are about 0.035-0.040%. When co2 level is raised up to 0.15% the assimilation and growth speeds up. That is what is said. Dunno if it have any special effect, but it cant harm them.
Yes I am using cfl for flowering. 125w ESL Growlight Red spectrum lamp for all plant flowering stages 2700ºK
Soil is ph.6.7 special for self watering pots.
I had basic nutrients for growth NPK 6-1-5 and marine oxhylium.
For flowering Captain Acids 2 component nutrient.
Component A NPK 0.5-8-1.3 Mg 2.6% K2O 1.6% P2O5 18.3%
Component B NPK 0-22.6-28.2 K2o 34% P2O5 52%