Exhaust started to get hot hot hot and engine seems to be running warmer than usual

Noticed the other day that my exhaust system is getting hotter than before very very hot causing a melt on my diffuser, system ain't moved, running scorpion res with decat pre cat still in place, engine also running a bit hotter than usual and fan is kicking in without even booting it

Any help would be great
How's the coolent level? Does the coolent look clean? How well is it running? What does it idle like? Are you using good petrol (v power, tesco 99, etc.) Or regular rubbish. My car doesn't run as well on cheap fuels. With cheap petrol it idles up and down with v power it's at a smooth 850rpm
How's the radiator, damaged or is there a blockage or leak in the system perhaps.
Engines run hotter when they run lean, is the fuel filter getting blocked with gunk or the injectors getting long in the tooth?
Coolent level is clean and at right levels, running ok when pressing clutch when driving revs drop a bit but go back to bout 850, using v power rad seems fine, I was thinking possible slight block in pre cat or something
Hook the plugs out and compare them.. Look for any signs of det. As mentioned above that'll put your exhaust temps up. Does it pull okay??