why did my fluency go down
yesterday my fluency was at 41% now it is at 39% what happened?
You need to revise the coloured skills. Forgetting words you haven't revised for a while is a pretty obvious cause of fluency decreasing.
WrigGeor is right. Keep working on gilding your tree, redoing your skills, and the fluency will stabilize. Try not to hover over words you don't know--use a dictionary and write words in a notebook. You might want to concentrate on one language at a time. My fluency fluctuates a point or two for no reason. Just ignore it!