If your having trouble with the ph down, you might try diluting it first before adding it to the water your going to use. A little goes a long way with that stuff. Personnaly I grow in soil and my tap water is 7.2 ph normally and I only need to add about 1 mililiter of ph down per gallon of water to get my ph to the right level, if I overshoot I just add more tap water in until its close enough. I dont add it every watering either because the natural processes going on in soil generally keep the ph at a proper level so water that is a little above the proper ph isn't really much of a problem unless your getting a lot of salt build up in the soil. I've never used dolomite lime so I cant offer an opinion on it but im sure if used in the proper amounts it should work for yah.