Hello, royboy210. Once planted, some hydrangeas can be slow to grow for several years. It is rare but it happens.
I have a 2 or 3 year old Masja that sounds like your shrubs. It does not grow as fast as all the others that I have but it appears to be healthy. How long have your shrubs been like that? One year? Two? More?

Normally, I try not to concern myself about growth on years 1-2 since it is best that the plant concentrate on developing a good root system. If your shrub was recently planted, give them one or two more years.

You sound like you have covered the bases: checked the soil pH, provided adequate water and sun, fertilized as needed. Make sure that the soil is evenly moist (so the plants are not going thru dry and moist cycles) during the growing season and make sure that there is no root competition (for water & nutrients) with other nearby plants.

Because you say that more than one shrub is having this issue and because that is quite strange, I offer one last suggestion. Do a soil test to look for either mineral deficiencies (check the usual nitrogen/phosphorus/potassium plus trace elements) and to check for things like too much salt in the soil.

Luis