Lets do some diagnostics here. I would get this app: [https://www.tunabellysoftware.com/tgpro/|TG Pro]. It will help you see the built in thermal sensors as well as the fan. You should get the full version to gain the most use here. Post a screenshot of main screen so we can see it too.
What are you running on your system? You maybe pushing it beyond what it was designed to do.
How much RAM do you have and free space on your SSD?
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=== Update (01/14/2017) ===
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The regions you marked off in Red are areas which would get toasty when you are running something CPU & GPU heavy. The areas are the PCH and the CPU power regulation circuit.
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First you might want to rethink what you are doing here. While the retina models are nice they are not a substitute for a desktop system designed to run heavy CPU & graphics intensive tasks.
Lets do some diagnostics here. I would get this app: [https://www.tunabellysoftware.com/tgpro/|TG Pro]. It will help you see the built in thermal sensors as well as the fan. You should get the full version to gain the most use here. Post a screenshot of main screen so we can see it too.
What are you running on your system? You maybe pushing it beyond what it was designed to do.
How much RAM do you have and free space on your SSD?