Welcome, Denise!
We could probably use a little more info to find a solution.
Are these brand new plants (less than a year)?
Were they damaged in the big freeze this last winter?
Is there any pattern to how they are growing or not--i.e., not growing in the shade or in the sun, differences between uphill and downhill, etc.
How and how often are you watering and feeding them?
That kind of stuff.