Gravel Problems!!! Why now?

Hello

I have been keeping FW planted tanks since 98 and have had them on
auto-pilot with good results for a long time. I used the Eheim liquid doser
and only do bi weekly pruning and water changes.

Since I last moved I have been scourged with BGA which is receeding with
sole KNO3/K2SO4 treatment along with increase water flow. It seems to
disintergrate into fine treads before leaving.

The problem after testing carefull is my water hardness rises continuously.
My tap water is 30kH and 30gH. My tank after a 50% water change is 80
kH/80gH (optimum) but several days later creeps to 120-140ppm levels. I
further investigated that the MgCO3 levels are barely rising and the CaCO3
are way up. This leads me to believe it is the gravel.

I bought the PetCO cheapo stuff with pink gravel accidentally mixed in. It
was new but may be wrong for FW tanks. I do see epoxy coated substrates that
look awefull to.

I used 50lb bags of quartz fine before with little problem. IT is not
available here. I am considering ordering Carib-Sea Amazon Basin gravel at
great expense. I live in Greensboro NC.

What is a good option here????