Aspirin may be worth trying for whites which I read somewhere:
With every wash, white clothes seem to become duller and greyer. So, how do you stop this process? It’s very simple; all you need is a type of medicine everyone probably has in their medicine cabinet. The only thing you need to make sure your laundry comes out perfectly white again is five aspirin tablets of 325 milligrams each.
Put the tablets in a large bowl or tub of hot water to let them dissolve. Stir this aspirin water until all of the tablets have completely dissolved. To make sure the tablets dissolve faster, you can also crumble them up before putting them in the water. Next, place the dull, white clothes in the bowl or tub with the aspirin water and leave them to soak there for eight hours. You can also just add a few aspirins to the washing machine, but the soaking method works better. After you’ve let the clothes soak, you still have to wash them in the washing machine like you normally would.