Why do dd's crop-tops go grey?

[GoodyGoodyGumdrops]

We separate our laundry by colour, and none of our other whites go gray. Why just dd's crop tops?

[dementedpixie]

Different material? Do you use liquids? They don't have bleaches so don't leave whites looking as white after a while

[GoodyGoodyGumdrops]

Whites get washed with powder detergent. Crop tops are cotton plus a bit of polyester and Lycra for stretch, just like many other garments.

[rollonthesummer]

Sweat?

Buy greys or black ones

[Bauble16]

Same as bras!

[GoodyGoodyGumdrops]

Do they?! I've had only beige or colourful bras for so many years that I've forgotten what white bras are like!

[LisaMed1]

I was told that using white vinegar instead of fabric softener kept whites white. I don't know about that but ds' school shirts and vests keep as white all through the school year and I use white vinegar. It may be just coincidence but it may be worth a try.