0 - 2 of 2 tags for response time

We are experiencing increase in response time of queries of a workload during a particular time of the day.What could be the possible reasons for this?How to analyse the root cause?
 
Appreciate your help!!

I need to know that what kind of Workloads should we set for Responsetime Goal and what should go into Throughput goal.
 
I know SLG are for primarily for Reporting and analysis, and mustly depends on these two factors described above.