Rusty marks on gi from washing machine

[Gingerlilly]

Does anyone else have this problem? My washing machine washes everythIng fine except my husbands white ju jitsu gi, it is a really heavy white canvas and always comes out covered in rusty marks that are impossible to remove. It s a real mystery why it only does this to the gi, but white sheets and white towels are no problem. Weve cleaned the washer with soda but its made it even worse.