This is my vote, especially if done within a few hours of the lights going out, especially if done directly on the nugs, especially if done to full drench.

I mean this with the best possible intentions, please use caution when foliar spraying during flowering. Most growers that use this technique stop by end of week 3, if not wk 2. The chance of problems is just too great & the potential harm is catastrophic. Just don't mess with it.

Re N def... if this is the nute issue, then quickly & immediately available through normal root feeds. In hydro will see the effect next day, if not same day. You don't need to foliar for N... very easily absorbed by roots, assuming pH balanced.

Just trying to emphasize that there is no need to expose yourself to the risk. Pics would be great to firm up the N issue as you mentioned brown spotting w the yellowing & this could be more K.

All the best & greenest vibes!

BTW, my gut feeling is that the core problem is pH related, but need more info...?