You are in the pol store loop.
Here's how it works...you buy a pool and the pool store experts tell you to buy lots of "shock" and algaecide and sequestrates and other potions and pour them in your water. All is well for a couple of years, except for the huge loss of money. You keep going back because your water looks fine and aside from a few green days, everything is fine. After a few years, in your case 4, the junk that the pool store pushers have sold you have polluted your water so much that you can't seem to "balance" your water anymore, but they sell you some more potions to get you by for a while. Eventually, they will tell you that your water is "old" and must be changed, oh and by the way, here is a $200 package of chemicals that you need to put into the water. again, for a few years everything is fine...repeat again. All this time, the pool store has paid their mortgage on their fancy vacation home on your dime!
Here on this site, the emphasis is on quality testing and adding ONLY and EXACTLY what is needed to maintain your pool water. No more "dump this in and see if it works".
Listen and learn and you will be A)Much smarter B)Self sufficient and C)Paying your OWN mortgage instead of the pool store owners.