On Wednesday, 25 November 2015 12:58:05 UTC, Dave Liquorice wrote:

Yep, 60 C wash will most likely have done that. I think the
mechanisum is that the red cells rupture, the heat breaks down the
heamaglobin releasing the iron they contain and you end up with an
iron stain (aka rust).

If vinegar removes rust from steel, perhaps it might shift it
from fabric?