Thanks for asking this question. I have only one thing to add - kid's swimsuits seem to be different than adults, at least in my experience. My daughter's swimsuits (from children's place and the like) all say machine wash tumble dry. And I do and they are fine. Mine all say hand wash hang dry, and I do and they lose shape.
I also have noticed that the suits I've bought in the last couple of years have disintegrated much faster than previous suits. I used to get 2-3 good years of swimming almost every day in summer out of a suit, now I am lucky if I make it through a summer. And I think I'm doing the same thing, which is hand wash with gentle detergent right after swimming and hang dry. Maybe I'll try the swimmer's shampoo.