I've found during VEG it's cool to spray and for me necessary. Neem oil, seaweed extract, bat guano tea or nutrient tea (all in light, light, light doses), have helped my plants and therefore yeld. I wouldn't like to grow without volar feeding in VEG.
Can be beneficial in First three weeks of flowering (gentil shower, nothing like the hose-down monsoon of veg)
A spray while in flower story: I have really beneficial L.A. Confidential Mom in flower (we are talking MILF of Marijuana, a true California Beauty). She had some spider mites (I think, could have been too close to the light) so I sprayed her with RO (Reverse Osmosis-distilled) water.
I broke the gentle shower rule (well, actually I just made it up) but it probably was a bad idea anyway. All that movement when I shake of the water (I should have been more gentile baby, I'm sorry baby, I'll change I really will), and water (weight) made her a little "shock" decreased growth, a bit limp. Luckily nothing too bad (I did heaviest some sagging lower spears though...initial test as we speak...Thank you God for all my friends who download good knowledge and kick-down good clones. Lower bud, no cure just dry and FUCING OUT OF THIS WORD). She was in her eight week from flower period start, I'll be taking her to 12 or maybe lucky 13.
For me no folar feed after Third week of flower and then the gentilest of RO showers only when absolutely needed.
Water spraying becomes a factor like any other in the big equation. My girl came through it OK because I treat her well otherwise.