I'd suggest that you give your plant a bit of a haircut in order to remove the dead flowers, fertilize it if you havent done so in awhile and give it a few days to recover. Calibrachoa responds very well and very quickly to being cut back. Since these plants last well into the fall, it seems a shame to toss them unless you're simply tired of them.

I did recently fertilize it, but I'll go ahead and cut it back and hopefully that helps! Thanks!