Yellow/brown staining on the pool floor

[ajsgolf]

33,000 gallon in-ground vinyl chlorine pool, no pool heater. Use a floater for chlorine tablets.
I have kept my chemicals balanced pretty well this year, just needed to make a few adjustments throughout the season. I've started to get a lot of pool staining especially in the deep end. My iron and copper levels are 0 and 0.1 respectively, according to my Leslie's report. Hope I don't get attacked for bringing my pool water to Leslie's. Images attached for reference. I bought a stain identification kit but it would be very difficult to try to get the powder in the precise location on each spot in the deep end. Any way I can get rid of the stains? Also, why are all these stains occurring? Also attached my latest Leslie's report for reference. I've added some No Phos related product to bring my phosphate level down. This is beyond frustrating.

https://www.dropbox.com/s/ltw775ieoiqvai5/Leslies.jpg?dl=0
https://www.dropbox.com/s/e9t1sdoqqy8dxyj/stain1.jpg?dl=0
https://www.dropbox.com/s/jlkbepn2sikk0f3/stain2.jpg?dl=0
https://www.dropbox.com/s/8cbylrzqnizo3ul/stain3.jpg?dl=0
https://www.dropbox.com/s/aveurrezjhcl9e5/stain4.jpg?dl=0

[Denniswiseman]

With a CYA of 64 you should be targeting about 9ppm free chlorine Chlorine / CYA Chart

Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continuous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well

Put a chlorine puck on a stain to check if it's organic (algae)
Put ascorbic acid (Vitamin C) on a stain to see if it's inorganic (iron)

Use these common products to balance your pool
Liquid chlorine (sodium hypochlorite or plain bleach)
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA