I don't remember where I read the info before settling on how I did it....but before I got my LED's and I was using my old 4 bulb, 2ft T4 fixture I would start swapping out some of the 6K for the 2700's when they started to show preflower. The thought behind it being that there is still growth going on while flowering is just starting, so the grow spectrum is still mostly in use. I'd then swap out one every week or two until running 3x2700K and 1x6000K to finish out. I think from what I remember some ran all 2700K toward the end, while some (like I did) like leaving the plant some 6K to play with.