Could be for a number of reasons. Did you prune them? when? Read the following post. You should get plenty of flowers being in Maryland. I live in NY and get blooms o plenty with minimal care.

Go to this webpage for more info on hydrangea care.

https://www.thespruce.com/identifying-old-fashioned-hydrangea-1402687

welcome to GoY.

its a coincidence that the previous question was also about hydrangeas. Have a read of the replies.

do you know which hydrangeas you have? Some species produce buds on old [this years growth] next year and if you prune too much in spring you remove the flowers. Typically the Mop and Lace cap types.
other species produce buds on new growth so prune in spring and the flowers form the same year. typically petiolaris [climbing ones] and Hydrangea Annabel.

I find the RHS advice really good.

https://www.rhs.org.uk/advice/profile?pid=516