My grandmother used to be a laundress and advised me to add a dash of soda with a detergent. Can not hurt for your laundry and your wash is white.
If your white wash is not as white as it should be, then you need to put hte clothes after washing down for a night on the grass, in the moonlight. Yet even in the sun to dry and the next day they will be white.
Fine white garments that are yellowed, lay them overnight in buttermilk. Works very well! did it with an old christening dress was awfully nice and white.
Cottons is sometimes soon. Do a Steradent (or other brand) tablet on top of the laundry in the washing machine and the laundry is brilliant white.
Steradent includes a bleach when used frequently affected by this so be careful fabric.
even add a bag of baking powder (baking powder sitting in a bleach: bicarbonate) in the detergent when washing your sheers. They may seem to be as white as when they were new, and they emit longer the dirt off.