Velocity has dropped, Could it be the mound i practice on?

Its in a public park and theres about 8 baseball fields where i live but all the mounds really aren’t on a slope they are practically flat.

In the videos youve seen i said my lead leg lands flat But it seems the mounds making me do that and i really cant build up momentum.

What do you think?

Are you getting clocked on that mound? Or are you pitching a different mound but you think pitching of that one is hurting you?