You may have been ahead of the game (only way to know I suppose is try store bought PH Up if you dare and try, lol), or your basic water chemistry may include sufficient buffers already. You'd need much more than a basic PH probe to test such actual numbers I think.

But also, my WORST case of ph dropping like crazy was when I was using plain RO water, no nutes at all. And it was dropping full points in a day (6 to 5 etc).

I'm glad to say though that now my PH is absolutely rock steady! Seriously like a miracle.

I think the bottom line really is that if you see CRAZY swings where you have to adjust the heck out of it one way or the other constantly, you very well may simply lack enough PH buffering in your *water* (regardless of nute brands), so a small bit of sodium bicorbonate could very well help stabalize it.

I've flipped over to 12/12 starting today, and replaced my MH with my HPS. These plants are going to be twice as big as I'd wanted them to be, but I can hope for a quick flower cycle I guess.