That's due to the salty shrimp GH/KH+ which is doing what it is supposed to.
If you don't want pH to rise you need to use Salty Shrimp GH+.
That fluorite substrate needs to go.
Depending on which version of Fluorite you bought, the red or black version, flourite has iron,
potassium and magnesium and high levels of calcium and sodium present.
I have a ten gallon aquarium with bloody mary shrimp. I have been using fluorite gravel and it keeps pushing up my GH and KH. I am now changing 20% of my water every week in order to try and slowly adjust it. My GH had been 15 and my KH about 10. I now have it down to GH of 14 and a KH of about 7. I have researched this on other sites and it seems that the Fluorite gravel will gradually stop leaching calcium. I have also been reading that a KH of 8 and above can cause problems with neocardina secondary to their shells getting too hard and the resultant white circle of death. My TDS can run anywhere from 230 or 240 after a water change up to 280 to 290 at the end of the week. Ph is 7.5 and above. I am no longer adding any supplements to the water.
One more question. I am using salty shrimp GH/KH premium aiming for a TDS of 100 after off gassing as the water I change with. I am adding it slowly over 6 hours. The distilled water has a ph of about 6.4 before I add the salty shrimp. After I add the salty shrimp to a TDS of about 100 my ph increases to about 7.5.