Heat issue after Marshmallow update

How hot? This processor in our phone runs hot. It is why Samsung used their own processor in the S6 phones. Sony used a heat sink to resolve this issue. Sometimes mine is warm but never what I would call hot.
 
I can feel the heat in my pocket and my battery doesn't last as long after updating to Marshmallow. So I'm trying to figure out if these are to separate issue or along the same lines because this has only been happening after Marshmallow update. It use to get warm/hot before if I'm power using it but not just sitting idle on the table or in my pocket. I don't really see any apps running in the background that would be different after the update but it's becoming very annoying.
 
How hot? This processor in our phone runs hot. It is why Samsung used their own processor in the S6 phones. Sony used a heat sink to resolve this issue. Sometimes mine is warm but never what I would call hot.

Did the clean install fix the issue?
 
I actually just did a factory reset yesterday and seems to working fine again with no heat issues. So, we'll see if that continues.
 
I also had this issue. Every morning after switching it on I could feel the phone quite hot in my pocket. Hot enough to make it really annoying. Did a clean install and although it was a pain in the back side reinstalling apps and restoring photos, contacts etc, it worked a treat. No more heating issues. Also the battery seems to be lasting longer. After 6 hours switched on,I was on 75% tops. After reinstalling marshmallow I'm normally around 90-95% . Best advice I ever read around here.thanks