need some help long run

I’m a newer runner (4 months in) and currently averaging around 35 km per week. I don't have a shoe rotation yet — I’m running everything in one pair: Xtep 2000 km 3.0.

The issue: Up to 10 km, the shoes feel fine, but once I go longer (around 16 km / 10 miles), I start getting persistent calf pain. Pace is ~6:00 min/km. I’m training for my first half marathon next month, so the long-run discomfort is becoming a problem.

Questions:

Has anyone here used the Xtep 2000 km 3.0 and experienced similar calf issues?

Could this be a shoe-related problem (stack, geometry, firmness)?

Any recommendations for budget-friendly daily trainers or long-run shoes that might work better for someone at my mileage?