Yes another thing I learned running AN back when was avoid mixing other brand products with it cause it wont always hold PH if you do. I quit using AN because it burns the tips of the leaves and makes my concentrates come out dark compared to CYCO PLAT. Have you ever had AN cause that weird necrotic burning on the leaves? I experienced it even with running much lower EC... Perhaps it's the type of Nitrogen(s) used?
This is one thing like about switching to tap. The plants seem to like the drift through the different ranges.
Do not I repeat do not use Fox Farms Coco.. CANNA, Mother Earth, TUPUR all way better options in no specific order. COco loko and their other soils have always sucked. Look in the plant problems thread for fox farms every other issue is a plant in Fox Farms. Unexplainable EC/PPM and PH from every bag.
I use other products like CalMag, plain p/k and a couple other things and never checked the pH as my $70 pH pen couldn't seem to read the AN nutes properly. Anything else it read fine so I just left it alone and never bothered checking pH again. The only time I had problems with burn was in winter when the RH could be 20% for months so at higher ppm they were sucking up more nutes with the extra water they needed which ended up manifesting as toxic salts buildup hitting about half way thru flower and frying all the leaves right up to the tiny bud leaves by harvest time. When you smoke that bud it goes snap, crackle and pop.
I've had the opposite experience. Pinegro "premium hydroponic grade, pre washed Coco". Came out at nearly 7000ppm from the bag. A brunnings "pre washed" coir block. Came out at 5900ppm and ph 5.1.