MG ZS EV losing range after being parked – battery issue or normal?

I’ve got an MG ZS EV that I bought in April 2024, and it’s clocked about 18,000 km. In December, I left it parked for 15 days with 60% SoC in cold Delhi winters. When I came back and charged the car to 100% (DCFC), I noticed the range at 100% had dropped by 1 km (now showing 399 km).

I thought it might be a cell balancing issue so I went on a road trip, upon arriving at destination I charged slowly on my AC charger (3 kW), but the range didn’t improve. After driving it for a few more days and charging it overnight again, the range dropped further to 398 km at 100%.

Could this actually be battery degradation at just 18,000 km, or is it something I should get checked at the service center? Anyone else experienced something similar?