In the Flash Rebirth comic it was revealed that Thawne generated a negative speed force when he ran, which gave him slightly different abilities (including a higher degree of time travel) than tapping into the regular speed force. I wonder if they're going to use this concept in the show as a way of explaining Wells lose of powers, that without pre Flash Barry generating the regular speed force, he has no ability to create a negative version of it. That could tie in to why he pushes Barry to be faster, once he fully powers up and taps into/creates the speed force Wells connection to the negative speed force will be reestablished.