Hi there. I am that in-experienced grower again that has very few teachers so I try to use some of you guys,but this time you might have a laugh or NOT. When I was first showed how to do this growing by a couple of very nice young men; they too were running around with expensive PH pens in there pocket and using ph-up and down every day. I noticed there was a lot of money put into their grow and that a lot of yellow leaves were all over in the veg and bloom rooms.So I went home and ordered me up one of these genius devices and bought the up and down products because I didn't know any better.But it all looked wrong following bad advice after bad experience so I got on the internet and looked for guys who have been doing this for 20 years and more only. The simple rules they had was to add 1 cup of fine lime per liter,1/4 cup of fast acting hydrated lime and be done with it.The PH stays put on an even keel at 6.8 all the way thru the grow. The only time that I became locked out of any nutrient was when I started getting chlorosis in the leaves at exactly 3 weeks into veg every time. I immediately started self-diagnosing a cal-mag deficiency and fought it like a 2 year old for over a year. Turns out that it had nothing to do with ph or cal mag. I forgot to add bone meal to my soil and locked the nursery out of phosphorus .Everybody talks about that nutrient being so important in bloom that I forgot how important it is for growing plants.I have never had anymore yellowing problems what so ever and have all my fans leaves in good health going into bloom. By the way, I gave the full bottles of up and down to a friend who loves to use it and kept the ph meter which I hardly ever pull out because it shows the same thing every time.In the end, it was all about losing the yellow leaves