Weird overheating problem

Experiencing a strange CPU overheating problem with my laptop. It seems to be struggling with basic shit it shouldn't have a problem with (and never did before). Even opening new tabs in a browser spikes the temp and the fan spools up. Watching videos in 720p or above and the fan runs constantly (not at full speed) - it never used to behave like this, but thinking about it now I've only had this issue since running W10. This machine was built for 7 so some stuff doesn't work since the changeover because Toshiba didn't release an update - but that doesn't matter because it was all Tosh specific stuff I never used anyway, like the eco button etc.
Core i7 processor, 16GB RAM, SSD's, dedicated NVidea GPU. I'm not experiencing issues with performance in a speed sense, it's a fast machine even by today's standards. It's just this overheating thing when doing basic stuff. I've pulled it apart and cleaned out the exhaust, which is now spotless. The fan seems to be operating correctly, no funny noises of doom so I can't see the point in changing that, heatsink is undamaged too. I'm thinking about changing the thermal paste, but I can't really see it helping (just grasping at straws).
Right now I have this tab open in Chrome, and another tab playing a video on YT. The fan is running at low speed (it never used to run at all doing this) but if I switch to the other tab where the video will be onscreen as opposed to here where I'm just listening to it, the CPU will instantly hit about 70C and the fan speed will increase. Turning the res down from 1080p to 720p will reduce the load and the fan will slow down. But the point is this machine shouldn't be taxed running 1080p video. Back when I first got it (2013) the fan wouldn't run at all playing Q3 with everything on maximum, it now does
Normally I can just fix shit my self, I know my way around a PC, but I'm a bit stuck on this one. Anyone had any similar experiences?
Core i7 processor, 16GB RAM, SSD's, dedicated NVidea GPU. I'm not experiencing issues with performance in a speed sense, it's a fast machine even by today's standards. It's just this overheating thing when doing basic stuff. I've pulled it apart and cleaned out the exhaust, which is now spotless. The fan seems to be operating correctly, no funny noises of doom so I can't see the point in changing that, heatsink is undamaged too. I'm thinking about changing the thermal paste, but I can't really see it helping (just grasping at straws).
Right now I have this tab open in Chrome, and another tab playing a video on YT. The fan is running at low speed (it never used to run at all doing this) but if I switch to the other tab where the video will be onscreen as opposed to here where I'm just listening to it, the CPU will instantly hit about 70C and the fan speed will increase. Turning the res down from 1080p to 720p will reduce the load and the fan will slow down. But the point is this machine shouldn't be taxed running 1080p video. Back when I first got it (2013) the fan wouldn't run at all playing Q3 with everything on maximum, it now does

Normally I can just fix shit my self, I know my way around a PC, but I'm a bit stuck on this one. Anyone had any similar experiences?