If I were you I would bypass the medium and go straight for the stoma to eliminate deficiency in flower it will only get exponentially worse as they use all the stored energy in their leaves. You need to displace the usage somehow.
Like I said worm castings will fix any pH problem. You could always use a handheld squirt bottle like the size of a breath spray that way you can be totally sure where it goes. I wouldn't worry about it though. I've foliared kelp when there was NO problem 3 weeks in. Never had a bud taste like sushi.
Neem could also be a good source of NPK, calcium, mag, sulfur a million other micros, antifungal and pesticide properties. Will not burn. Will not change flavor. Guaranteed.