when i first use neem i hit all my plants three days in a row, then go maybe once every week or two as i see fit.

Safer brand products also make a fungicide, an insect killing soap, and a caterpillar killer all in concentrate for around ten bucks each... i mix one cap of each per gallon and foliage spray once a week or as i see issues arise.

i cant guarantee that this will fix your issues but its done an incredible job for me year after year.i hope this helps.