Rustoleum makes a great rust remover.
This post might be helpful Kenneth
Perhaps one of these remedies will help. https://www.thespruce.com/remove-rust-stains-from-toilets-tubs-4109490
You need to be careful with acrylic tubs. If you use anything too abrasive you will damage/scratch the acrylic. Bleach is NOT something you want to use on acrylic tubs. These articles suggest a solution/paste of lemon juice and salt to remove the rust.
Seems like you have to be very, very careful!
I was able to remove a rust ring caused by a shaving cream can from an acrylic tub by gently scrubbing it with a bit of white toothpaste and a smooth cotton cloth. It didn't mar the acrylic at all.
If you try The Works from Dollar Tree, get two fans going in there & wear gloves.
it does work, but the fumes are bad.
CLR add it on the spots let it sit over night maybe add paper towels on top of the spots so the CLR sits on the spots you could get CLR at Home Depot
Hi Kenneth, nothing abrasive on acrylic, try this, hope it helps
Try WD-40 on a soft cloth - it takes off rust! Good luck!