I suggest you concern yourself with getting the pH correct, and let the ppm sort itself out ... find a different water source, perhaps ... for some weird reason, I couldn't get my ppm over 900 or so, (using Fox Farm nutes), unless I really went crazy with the dosages

... but, I guess the plants couldn't understand it, either, because they did just fine ... your GH nutes and 'pH Down' are quality products, I don't see any problem there ... good luck
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