Hi Suzy!
Oh my goodness, your shop is fantastic! Your yarn is beautiful!
My sales were going well, mini skeins selling pretty much within a day of uploading and then it all of a sudden stopped. No sales for about 3 weeks, so I asked the same question as you in this forum and was told that it might be a seasonal thing.
However, the 'dry spell' only lasted a few weeks, it is all back to normal. I think adding a lace weight yarn is a great idea. How about putting that in the first 3 words of your title ( which are the most important)? So start your title with Lace Weight.
Play around with your titles and tags, I am sure the sales will pick up again.
Good luck! :)