Welcome to the forum!

Bill, sounds like you're dribbling chems around the perimeter that are reacting with another chem in the pool or some organic is washing into the pool in the deep end and reacting with a chem in the pool. I think the stain you see on the wall will react well (i.e. go away) with a little high concentration of chlorine.

The rust stain can be removed with Vit C (ascorbic acid).

Lisa, sounds to me like he was kidding, and venting - we all love our kids - even when they do things that annoy us (Oh, I've got 'war stories"... )

Hope you are well!