[Helios 300 PH315-52] GPU thermal throttling at low tempertures

I am experiencing lower gpu clocks (~1500MHz) while playing games like Valorant and Apex Lengends. I play with Afterburner in the background to monitor the system throughout the gameplay. Recently I am noticed the GPU temperature limit and lower gpu clocks eventhough my GPU temps were around 64*C. I checked the GPUz and PerfcapReasons was showing Pwr,Thrm. Is it normal or my GPU is thermal throttling? 

Config:
(System repasted with Kingpin KPx)
CPU: i5 9300H (undervolted -140.6mV & underclocked  to 3600MHz)
GPU: GTX 1660Ti 

Temps:
idle:
CPU : 40-51*C
GPU: 39-43*C

GAMING : 
CPU: 70-82*C
GPU: 64-72*C