I honestly sometimes spray plants right under the HPS if I feel it necessary. If I think its a big deal I just slide em out from under direct light until they dry off. Most foliars will dry very quickly without residue....I believe JK was saying that he wanted to once and for all say that water on plants with lights on does nothing. I haven't seen any "burning" issues with droplets on leaves or spraying with lights on. Like I said, just slide em out from direct light, no need to break the light cycle or dark cycle just to spray. And mist anyways, i spray a fine mist when i spray... better coverage and dries more evenly anyways.
Spraying and watering right before dark cycle can cause other issues too though, so do plan it early in the light cycle so you don't get rh rise and fungal issues with lights off.
and fwiw i see more climb in rh from heavy watering than foliar feeding or misting. It breaks down to Shady's link to the VPD, its relative to whats capable of being taken in and put off, not whats actually there.
BTW- Shady, great link on the VPD bro. Think that quantifies what I've been thinking and may resolve any issues I have as well. Great read, everyone should read it.