The best buds always seem to come from plants that drop all the fan leaves the last week or so of flowering...Remember, cannabis plants complete their life purpose in one big finale. They have evolved to grow, flower, & reseed the earth in a single life cycle and will use up everything they have inside to complete that purpose the best they possibly can. When they are all done, you do not want them to have that "green" in them anymore or smell like hydro nutes...I have heard of many people only using plain water for the last 7-10 days to really help things along and let the plant release all that stored up energy from all those primary & lower leaves as much as possible...you want the plants to do exactly this to help give you a clean and smooth smoke and properly burning buds..pronounced phosphorus/potassium deficencies manifest as nice purples & reds in the end also in alot of indica based strains which is really nice too...Yield is really not affected if you time it right and know your plants/strains normal completion cycle. Also the dropping of big shade/fan leaves can open up lower bud sites to much more light and help them fill & swell out at the very end and even increase your overall yields/quality. Hope this helps..just my opinion of course, never actually tried it.