TTFB - 3063ms on AWS EC2 Instance

We recently switch out hosting from one AWS system to another one (switch the region from Asia to US-east).

The old system is very different from the current one. The old system is one EC2 instances that hosted multiple website and configure using cpanel.

This new one is having a load balancer that round robin between two instances and the websites files are hosted on a Network File System (EFS in Amazon). Instances are also connected to a Relationtional Database.

Once we switch over the hosting of one of the website to the new system. The site now takes a very long time to load (20-60+ seconds). I tried to optimize the page as much as possible (through google page insight), but the load time still takes forever.
http://www.webpagetest.org/result/171024_NE_d77e1e3fcaae0dd2a982af00fdebd17c/1/details/

I’m not sure how i can fix this issue.

I very new to server administration, so this is all very new to me.
Any advice on how I can go tackle this situation would be very helpful.

Thanks in advance.

So it turn out that one of the instance had a steal time % of 90.
I rebooted it and the load time improve drastically.