no real clue on Schultz. Seems like he needs a year in the weight room.
Jarwin might catch a little but isn't very good blocking.
I have not seen one TE on the team that can block in the open field.
Swaim and Gathers seem to in-line block some -- not Marty B level, but at least some.
Basically I think they all need to go to "blocking in space" class, and even then, I am unsure if you actually have a good TE.
My best guess is that Dallas doesn't have a teacher that can teach blocking in space, and these guys have never had to do it.