I was wondering if anyone could tell me what this bush is. I'm in zone 7. It has small bright yellow flowers that run the length of the stems which come up from the ground like a fountain, with lots of individual thin ones in a bunch comprising it. Right now it's about four feet tall and was until a few weeks ago was very pretty but all the flowers have fallen off it at once and all that's left are green leaves.

I suspect it just got too cold for them and had bloomed too early but maybe I need to give it some special attention? If I know what it is, I could find out.