[Urgent] Web front-end overload - How to investigate?

Hello everyone

Our farm (SP 2010 foundation, sql server 2014) suddenly using huge resources on peak hours while DB's CPU and Memory usage less than 50%. I don't know which factor impacts it. My farm have 2 WFE, 2 APP and a cluster DB2.

WFE environment below:

• Windows 2012
• Trend micro enpoint
  
  WFE1
  

WFE2

How to investigate and resolve the problem?

Thank you for any suggestion