Actually, I turn my fans off, leave lights where they r, and spray... These lamps r actually alot more resilient than alot of folks would have u believe. Ive worked extensively with all types of HID's for the past 15 years, and have had them blow up in my face, and its usually been because of oil, from hands or some other oil-producing source, and not so much water...
I'd find a horizontal lampholder/reflector if I were u... These lamps emit most of their light horizontally and for growing, should be utilized that way... The way yours r turned is the way I hang them in warehouses for people to see shelves and shit, not to grow awesome nugs... So, some of your light is probably getting wasted...
It doesn't do anything for the plants to be sprayed at night, except set up the possibility for mold to set up... But with fans, mabye ok... But, still the stomata will not open up to absorb anything via foliar spraying at night, only when light is on can the leaves use this...
First thing in "the morning" is great, sometimes I'll even mist them JUST befor the lights come on to mimic dew in nature, and then they quickly absorb whatever they want to, evaporate the rest, and the coating helps to protect against pests and such... Light's on when foliar feeding is the key thing here...