sounds like youre having all the same trouble i was bro. ph is fickle bitch and drops arent that reliable.and it sounds like your water has some funk goin on. you need to know whats in your water. is it heavy in salts or metals? that ruins ph readings.
ive been screwing around with it since november and im just now getting somewhat reliable conclusions. in my case i use ffof and if i filter my water and adjust the ph, my soil runoff ph will rise and so will the water when it sits. if i do nothing to my water at all
my soil runoffs will be very low. and that is using water at ph 9.3. the runoff will be in mid 5's. so to compensate for that now im boosting my ph a bit, sounds counter-intuitive but so far the plants are responding. im not saying that this is a solution for you but you need better info on your water than drops will give you and not just ph you need to now your ppm and ec levels. a good meter is a necessity.