Has your fabric got white crease marks on it ?
This is Crazing
Crazing happens when the material you are using has been treated with a finish that gives the fabric a water repellency.
It usually happens when you fold or crease your material - so for example when sewing. It is completely normal and will eventually disappear once the material relaxes.
It is common on many solution dyed fabrics or fabrics with a heavy coating.
A couple of things you can do if you are using these fabrics to make your Biminis/Covers/Enclosures is to firstly keep the fabric stored on the roll and secondly try to roll the fabric under the arm of your sewing machine rather than fold it.
As we said earlier it is normal and will go as the fabric relaxes or ages.