Expert Haze DWC

Plenty going on this week, again. Lost a handful more large leaves to the browning - see photo - but this issue seems less problematic than last week. Without intervention, the PH seems to naturally tend towards that of the local water, about 6.3. Last week I brought it down to 5.9, with PH Down, but now it's back at 6.2. I will leave it at 6.2, because plausibly stress due to these PH variations is the cause of the leaf browning. EC has been steady at around 1.1 mS/cm, give or take 0.1. Seems enough for the plant at this stage, although the Ionic Hydro Grow guidelines suggest I should be at 1.5-2.0. A commenter said the recommended dilution for Ionic Hydro Grow is 5-7ml per gallon, but on the bottle and on the Ionic website it says 5-7ml per litre, so I'm confused. 5-7ml/gallon would give an EC of 0.3 mS/cm, which seems far too low, but who am I to say? (This is my first hydro grow...) Gone to an 18/6 light schedule, since we'll soon be heading to 12/12 and going directly from 24 to 12 seems likely to cause stress.