Got new stains immediately after an ascorbic acid treatment. Help !

I have a 11-year old fiberglass pool. I’ve periodically had stain issues, and had been successful with them in the past using Jack’s Magic Stain Solution #1 (“the iron, cobalt stuff”). But I had some areas of relatively minor discoloration that it didn’t successfully treat. I read on various forums including this one testimonials from people with fiberglass pools who had great success using ascorbic acid once a year at the beginning of the year – they said it made pool look brand new again.

SO I tried it – pool water pretty well balanced, and chlorine under 1PPM. Water pretty cold – about 58. I used 1.5lbs of Ascorbic Acid (using brand “Natural Chemistry Stain – Free”). Very quickly some yellow stain streaks appeared on steps and near edges of pool – seems that the acid caused something to come out and into pool sides. It does not brush out.

Thinking it might be iron, I tried some of the Jack’s Magic Stain Solution #1 at one spot – but no success.

Ideas as to what the acid caused to happen, and more importantly, how I can recover ? (MY pool looked much better BEFORE I tried the ascorbic acid. I of course wish I had just left well enough alone.)

Thank you.

Little more info: Even though they seemed to be the result of some action of the ascorbic acid, I tried the trick of a Vitamin C tablet to see if it would do anything. I know this works well when its iron. In this case, it had no effect at all. So I dont have any good ideas on a next step - hoping someone here might. Thank you.

not sure what the problem is, but the vitamin C doesn't surprise me- I think its ascorbic acid, so if the chemical form didn't work I wouldn't expect the vitamin form to work...
Have you tested the water for metals?

The pool does not test for the presence of metals. I too had little expectation of the vitamin C doing anything (yes its ascorbic acid), just wanted to rule it out.

My current hypothesis is that its organic in nature. I dropped some chlorine in one shallow area of the spot, and it cleaned up. The area near it had been yellow too, and it changed its hue to more of a gray. It looks like its just dirty there, but of course does not brush up.

I brought a water sample in for testing. No metals were seen. But phosphates, TDS, and cyanuric acid are all pretty high. I think my next step is going to be a partial drain and refill before I try to just attack with a bunch of chemicals. After partial refill, I'll test again and shock if looks like organic based.

I'm a bit perplexed about the high phosphates. I routinely use "Jack's Magic The Pink Stuff" as a sequestrant, as I have had iron stains in the past. The label really doesn't go into the details of it, except that its not acidic. Does anyone know if it adds phosphates ? (I'd probably use it even if it did, as its been good for me. I just want to understand any side effects it may have.)

If anyone has any other good ideas, I'd love to hear them. Thanks.