Is it possible you are 'over' teaching.
Explaining too much and for too long?
Show, quick and short explanation, show again and let the students work it. They will struggle but struggling is important. They learn what not to do as they learn what to do. After doing several reps 10-15 show again correcting only 1 or 2 things at the most corrections. Then again let them struggle.
Be encouraging,
Be excited when the students do something well. Doesn't have to be perfect just better than before.
Use phases such as:
"You've almost got it" rather than "That's wrong".
"That's better" rather than "No, it's this way, now do it again"
"Great to see you working it, here's another way you can do it also.
One of the worse things an instructor can do is to get in the way of the student having fun learning.