I definitely want to try the 4K bulbs for a whole cycle, the 3K ones too, but I really want to see what the 4K bulb will do in flower. I think the enhanced UV from that spectrum will help give the plants greater trichome coverage, even if that may mean slightly smaller yields. It would be cool to do a full grow with the same variables for each grow, except using the 3K for one and the 4K for the other. Have you used both bulbs for veg/flower?