I have a 6-7 month old ASUS TUF Gaming FX505GT Laptop which I use for primarily gaming, and programming. I have 3 built-in settings for controlling fans' speed which are Silent, Performance, and Turbo. The Turbo mode is only available when the laptop is plugged in. It takes the fans' speed to about 6000 RPM. For the last couple days, even when plugged in, the fans haven't been going past 3500 RPM. I noticed this after a Windows Update, a few updates to the BIOS, and a couple of Sound Driver updates. However, the weird thing is, when I launch a specific couple of applications (Assassin's Creed Syndicate, VLC Media Player), it will boost up the fans to their full capacity, while when I play some other games (Tom Clancy's Rainbow Six Siege, Discord, Android Studio, and majority of others), it won't do so, causing the system to slow down terribly.
I have -
1. checked NVIDIA Settings to make sure my system is using appropriate GPU for required apps
2. checked that there are no further updates to BIOS, Windows, etc.
3. set fan speed to always Turbo