CYA too high

24000 gallon, vinyl, mesh cover. I tested the water and CYA came in at over 100. Took a sample to pool store and they had it at 126. I was surprised because I drain about 5000 gallons and snow melt etc replaces. 2 years ago I was on 100% liquid, last year, had to go to 3" tabs because I was not home much. So tabs likely are the issue? but I was still surprised at how high. Other measures, free chlorine 2. Total chlorine 2.8, pH 7.1, Alkalinity 46.

Do I need to start draining water? I am on a well with iron. Is Pool Magnet OK with this much added, or should I have some water shipped in.....and how much do I need to replace? I assume I can't take more than a foot and a half out (7200 gallons). (36'x18'x variable from 3 to 8'). Thanks for the help.

Tom