White marks on dark clothes after being washed

[WestYorkshireGirl]

Every time I do a darks wash the clothes come out with white powdery marks all over and it seems to be getting worse. I use a gel in a ball and use the correct amount. Also use good quality softener - a capful. It makes no difference what programme. Any ideas?

Try halving the amount of detergent, you don't need as much as the pack says usually.