It simply means that temperatures are dropping ion those zones.

1. You can try giving a higher/ realistic temperature initial conditions.

2. Try giving more relaxation in energy equation

3. Try starting with adiabatic walls, when the flow stabilises, use this solution as an initial condition.

4. Use k-epsilon model initially till you get somewhat stabilised solution, and then only change the turbulence model.

Use any one of the above or a combination, whichever works for you.

Best of luck!