whink rust stain remover, bronze plastic bottle, usually top shelf grocery store. Used it for years on COLORFAST fabrics, white ceramic and on a cloth applied to carpet. Follow the directions implicitly. Has removed many rust stains for me. Had a washer with chipped drum. Would get tiny rust stains from that chip. Whink removed immediately. One bottle lasts many years for small spots.
Make a paste of lemon juice & baking soda, rub on and then hang outside in the sun. I used this on a vintage sweater set and it worked like a charm.
I have also used lemon juice and pour salt on top of that and place in sun. Works best on white!