I would drain most if not all the water, if the water table is below the pool, and start over with a new batch of water so you can eliminate the use of sequestrants. If you want, you could chlorinate with tablets, no mineral cartridges, until the CYA is in the 30-50 range. Once the CYA hits the new target switch over to using bleach.
Follow our methods and you will avoid sequestrants, weekly shocking, and you will have sparkling clear water all year long.