Ph problems

So I am having a ph problem. All my plants have a ph of 6. Doesn't seem to matter what ph I put in it comes out at 6. I've tried 6.9 - 7.6 and even 8. It all comes out at 6. My plants are doing ok but you can definitely tell they are having low ph problems. I am very confused as to what is going on. I am using sunshine mix #4 soil which I always use and have never had a problem with before. My plants are definitely ready to put into flower but I would like to take care of this first. Any thoughts or suggestions?

What is your waters pH and ppm out of the tap.
You are talking about your run off?

Yes talking runoff. Comes out of the tap at 8 ph and 230-260 ppm. I just find it weird cause I have never had this issue before.

Is there something in your soil that is buffering the soil to 6 ? Could the ppm in your water be reacting with something, causing a lower pH? What kind of pH down are you using ?

Root farm. Never had a problem with it before. Not sure what could be in the soil but must be something. Like I said.... I've always used this dirt with no issue.