I think it has been caused by drying on the drying rack inside over winter, it has been a horrible winter, but I can feel spring coming so back on the line we go at our last house I was able to pop the drying rack on the back verandah in the the breeze/sun and just move under the cover if the weather turned but we don't really have the ability here (yet, we will by next winter hopefully)

Thanks for your help!