Macbook Pro very slow on Dual monitor setup?

I have my MacBook Pro (Retina, 15-inch, Late 2013), 2.3GHz, i7, 16GB DDR3 Ram with macOS Sierra version 10.12.6 connected to dual monitors LG. My laptop is connected to the charger, so I can close the lid and use just the 2 external monitors.

My issue comes gradually every time. First 20-30 min of usage seem normal, it works fine. After that the CPU goes crazy for some reason. The Activity Monitor shows "kernal_task" at over 500% CPU usage all the time. Which is not normal at all.

I don't know what's wrong or how to solve this issue. I never have this problem when I use my laptop when its not connected to external monitors. Ideas?