I think it's a bit premature to say they "quit growing". It's only about a month into spring and harvest isn't for some months.
Plants in general do not like to be watered a lot, least of all hops which tend to burrow deep to find water. Plants that are overwatered tend to slow down because they have what they want, but not what they need. What do they need? Only enough water to live and perhaps something to eat. If MO is like NJ this year, we've had plenty of rain and that could be the culprit.
My best advice is, if you have been watering them, stop watering them for a couple weeks and maybe cut them back a foot off the top and give them a reason to grow.
It's no different than having free room service on a vacation. Why go elsewhere when you have what you need right in front of you?
Hops tend to grow themselves. Aside from fertilizer, you can kind of leave them to their own devices unless there's a drought.