How do I get white stains off my black sheets? I wash at 40° and have tried different detergents (usually use liquid) but to no avail - the sheets come out of the washing machine with the same snot/milk/whatever stains as when they went in. It's not just the sheets, though, I put a pair of black trousers in with them and they seem to have acquired gloppy snail trails of their own in the wash. The weird thing is, it's only this type of stain, if I put in whites or other coloured all the nasty food stains come out.
This doesn't happen to synthetics, only cotton. I tied switching from liquid to powder but nothing improved. I don't use softener either, only vinegar.
Can anyone help? I'm sick of my bed looking like there's been a snail party on it.