Bought a cotton dress in Oxfam and then realised that it has yellow discolouration patches. They’re in random places so not totally sure if they’re sweat/food/age (as it is 1960s). It’s pale cotton but doesn’t have washing instructions. A normal wash didn’t shift them but leaving it in the sun all day has faded the marks a bit. Any other tips to get rid without trashing the dress? Thanks!