If their is any KPI which is not performing well what would be your actions ?

@yuhuisg has some good advice here.. this question can be open to a lot of possibilities depending on which KPI you are talking about...

Now, if you noticed something like your PVs or Vs or UVs drop drastically "overnight" that might indicate that something broke, and it's time to dig deep and test it... however, it could just be seasonality or as mentioned above global recession, etc... a lot of how you deal with this is very dependent on the type of site, the type of KPI you are looking at, if your site has a behaviour pattern tied to seasons (i.e retail will have peak times of the year where there is a lot of purchases, and other times of the year that are really slow). 

If this is a completely new feature that isn't performing... it could be an error in how the tracking was set up, or it could be an issue with the site not promoting that feature well... maybe users just aren't finding it... this may require a group effort of designers and marketers and analytics to come together to analyze what might be happening.

I understand if you don't want to share specific details here about your setup, but (I can't speak for yuhuisg) but I would be happy to help you in a direct chat if you would like to share more details about your concerns. Or maybe yuhuisg would like to take that on, since he beat me as the first to answer 🙂 (he is really good and knows his stuff too)