With Flora 3 pt. ,I usually go with 3/4 recommended for veg, or you can jump to Lucas Formula 8micro and 16 bloom per gal. with 20 gal. res. you can use addback method ( until replaced 1/2 total) then change res. so after replacing 10 gal. (change Res.)- Daily- Add water as needed, then drain 1 gal. mix nutes, pour back in, wait awhile, check PPM & PH( I've been targeting 7-800 PPM for no burn/no def. solution- so far, no issues). Cal mag is primarily for RO water, but if stems are red/purple, can use small amount but as Bos said contains Nitrogen- same with grow nute( thats why Lucas doesn't use- theres enough in the Micro