What are these yellow brown spots at the bottom of my deep end??

[Damonsmith]

16k gallon chlorine pool, 2 years old, gunnite and stonescapes plaster. Levels are good, first time seeing this…

Only in this one area in the deep end. It is also the only area under a tree.

I did recently add Leslie’s chlorine tabs - which were about 18 months old, not sure if that matters.

I did the vitamin C in sock trick and they faded away a little it then came back a week later.

 

[mknauss]

Welcome to the forum!
If vitamin C removed them, they are iron. If they came back, they are likely wire ties from the rebar that are close to the surface of the plaster. Best to just use vitamin C in a sock on occasion to remove it as necessary.
When you re-plaster, the wire ties can be dealt with.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[Damonsmith]

Welcome to the forum!
If vitamin C removed them, they are iron. If they came back, they are likely wire ties from the rebar that are close to the surface of the plaster. Best to just use vitamin C in a sock on occasion to remove it as necessary.
When you re-plaster, the wire ties can be dealt with.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

Welcome to the forum!
If vitamin C removed them, they are iron. If they came back, they are likely wire ties from the rebar that are close to the surface of the plaster. Best to just use vitamin C in a sock on occasion to remove it as necessary.
When you re-plaster, the wire ties can be dealt with.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

Thank you for the reply! Any idea why they would just start showing up now after the first couple of years?

Welcome to the forum!
If vitamin C removed them, they are iron. If they came back, they are likely wire ties from the rebar that are close to the surface of the plaster. Best to just use vitamin C in a sock on occasion to remove it as necessary.
When you re-plaster, the wire ties can be dealt with.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

ty! Update I just went in with a chlorine puck and rubbed it against the pebble and it cleared up pretty quickly, does that mean mustard algae or something similar?