Could biological powder be shrinking my lycra clothes?

[megletthesecond]

My faithful black work leggings have become tight. Wet suit tight. It's even hard to get them over my feet.

I'm underweight and have lost half a stone in the last year (bowel op). My other clothes are fine and some are too big. Except the bloomin' leggings .

I started using biological washing powder last summer to cut back on plastic use and I wonder if it's degrading the stretch in lycra garments. I wash them mostly at 40°, sometimes at 30°.

Do you use softener? That's apparently not good for lycra

No.
It's lidl washing powder. I wonder if it's the brand.

Are you tumble drying or ?

Non bio is available plastic free - try Tesco own brand

We are keen cyclists & I run, so lots of lycra clothes
Have used only Bio detergent for 12+ yrs.
Nothing has shrunk. I was wearing some 20yr old leggings today.

Never tumble dry either.
My shiny, sporty lycra is ok, had to buy a size down running legging as I've lost weight. But the cotton /lycra mix is what's suffering. It's weird.

ps: we use Lidl Bio, too. Mostly colour, technically, but that is a Bio.

Do you wash at the correct temperature?