2018 RB 15' Extreme Temperature Issues Over Time

Hi,
so I've had the 2018 1070 advanced model for a few months now and I've gradually seen my temps get significantly worse. For the most part, I understand that laptops generally get hotter as they age, but this has become extreme. When the laptop was new and running in balanced mode, I was looking at mid 80c on the CPU and low 70s on the GPU (with a -0.145 undervolt on the CPU). The performance was good, the CPU was maintaining around 3.1 GHz in-game and I was pretty content. However, this only lasted around 2 weeks; gradually, my temps were going up and up with essentially no change to my application flow. Now, while playing games and no matter what I do, max fan, balanced mode, undervolting GPU/CPU, the CPU temp goes up to 100c and stays there. This is concerning because this laptop isn't old and was pretty expensive; I keep my gaming session short because I'm concerned about the effect maintaining those temps will have on the longevity of the laptop. I have no idea what to do, but it's incredibly disappointing. If anyone has had a similar issue and has found a solution, please please let me know.
Thanks in advance.