Brown stains again and again

[lilliswan]

I have a 12,800 IG, fiberglass pool. We have public water. Brown staining along water line developed about 2 weeks ago. Water was clear with a green tinge. We use stabilized clorine pucks in an automatic feeder. Took a sample to local pool store and was told no metals, all levels were good, store suspected organic stains, was told to use asorbic acid only and filter 24/7 and then shock. Stains cleared immediately, water cleared! 24 hours later the entire pool was covered with a dark reddish brown stain. The surface was slippery but the stain beneath wouldn't budge.
Since then I have visited 3 additonal pool stores and gotten a ton of bad advice. Most of which i have ignored. The stores in this area are staffed with kids on summer vacation that tell you to add this without even listening to your explanation of the problem. When you ask them an intellegent question they can't respond without handing you a bottle to purchase.
I have been reading your forum and trying to follow the advise but my pool is still not improved. Ph and cl have been maintained stabile although i wonder if my high CYA requires a higher fc, but if I raise the fc it seems to send the metal back to the walls.
As of today I have tried the stain removal followed by metal out and 24 hours later floc. Tried this 2x. only floccing the second time. I have also been adding liquid cl since my cya is high and backwashing at least daily. seems to pull the metals off the wall for a day or two and then it starts to settle back onto the surfaces.

As of today water is clear but green. Heavy stain at water line and on seats, steps and bottom. Next i will see it start on the walls.
Chems are TC .3, FC 1.4, CYA >100, pH 7.4, TA 220, Calcium 230, TDS 500 as of today.

What do I do at this point, I am considering draining 1/2 water to get CYA down and replacing the sand in the 2 year old hayward filter and taking the heater off line. Balancing and praying. Any suggestions? Also of note heater is a titanium unit. Any help would be appreciated.