Take the chain off the rear sprocket, and try to bend every link. Maybe you will discover the link that you can hardly bend by hand. If you find it, try to use WD-40, see if the O-rings are missing, hence no grease, hence tightness.
Just to exclude one silly possibility... The area around the front sprocket is very hot because it is very close to the engine. If you check the entire chain after a ride, it is only natural that the area of the chain around the front sprocket will be hot if the bike sat for a few mintues after you finished the ride. The rest of the chain will be cooling off during the same time. As you start checking the chain it is mostly warm or cool, until you reach the area which spent a few minutes next to the engine.