Test the CYA with your kit. If your CYA really is 90, that is actually already too high but you don't really want it any higher. Those tabs will continue to add CYA. How many do you have left and are they wrapped or unwrapped? A better choice would be to just use plain, unscented bleach. Walmart's generic is what many of us use.

Borax is 20 Mule Team Borax --- laundry aisle at Walmart.

Get rid of the mineral cartridge. You don't want metals added to your pool.