This is new set up about a 5 or 6 weeks

Not to sure but I think drift wood lowers PH.
tank looks good btw.

driftwood , you fish will appreciate it and will lower ph

using an ro filter is a good way to keep your water between 6.5-6.8. It also helps with lots of other issues. I would take some sand from the tank and put it in a container with a power head or air pump with some new water from your tap. Test the ph first, then let it sit for a day or two, and if the ph rises again then you'll know where the problem is. try the same with your big rocks if it turns out not to be the sand. I wouldn't put anymore ph down in there, not till you find out what the problem is.

agree with harvick and s m . ph out of my tap is over 8. i have several large peices of wood and the ph in my american tank never goes above 7
i would also try Justin's idea for testing the sand and rocks. good luck Russell
tank looks great by the way

Thanks every one for your in put I'll start trying some testing.

if the sand has crushed limestone in it that would be it .

Tank looks great Russell. Good luck getting the prob under control.