do you use filtered water in your iron? If you do, it could be that as the filtering process leaves iron deposits in the water which obviously turn the water brown when it is boiled. I ended up chucking a big steam tank iron away as I killed it with this kindness....:-(
You could try removing them with ordinary vanish and a scrubbing brush or leaving them in a sterilising solution for a short time. Not too long though or the colour may bleach out, but then if they are ruined anyway? Alternatively, re-dye them a darker colour, black is very in, or any dark colour really, navy eg.
good luck