Hi RuslanRobot,
Sorry for the delay I thought I responded but don't see it.
The KStep MOSFET Junction Temperatures are rated for 150C and KFLOP DSP for 90C so that should be well within margins.
Without significant airflow across KStep that would be expected and should not be a concern. KStep uses very efficient MOSFETS (17mOhm) to operate without a fan or heatsink but at max current will still be somewhat warm.
Nice thermal imaging!