Whites

I don't know if this will help Joelsnan but I always put a Colourcatcher paper in with each wash. This will need to be either pinned onto something big or placed inside a laundernet bag - or it may block the pipework.
I suppose the colours are bound to deteriorate in time though.

I find that unless the whites are pure cotton they discolour at high temperatures.

Whites need sunlight IMO

Plus hot temps "cook in" biological stains so hot washes dont = cleaner looking clothes.

I agree, rosenoir. Cotton and linen will stay properly white if washed at high temperatures, but any fabric with synthetic yarns in it won't stay white. It's the nature of the beast, I'm afraid.

There used to be something you could put in with net curtains to help keep them white.

I have a white duvet cover, pillow cases and white cotton fitted sheets which are still as white as the day I bought them 17 years ago. I don't have any special secret, although obviously I always wash them separately. Nowadays I wash them with an Eco Egg, usually at 40 or sometimes at degrees.

that should read sometimes at 60

Re. another thread - add soda crystals.