Now I do. With adding the cal mag you are adding lots more N without adjusting your K to keep the correct NPK ratio of mega crop. I use protekt 0-0-3 to rebalance cal mag 2-0-0 if needed. I would stop the cal mag and jump the MC up to 5.5gm-gal.
Taking clones during flower can cause problems. Cloning is the most stressful time a plant goes through add that with the reversal to veg. It can be done but then you worry about the possiblity of the plant turning hermie.
As long as you allow the plant the correct amount of darkness switching from day to night is not an issue. If I have to switch I do it during its dark period and so it gets the extended dark and not the extended light.