We have had them for about 3 years and this year only one bush has one flower. Do they need something?
My Hydrangeas Are Not Blooming This Year
Your hydrangeas probably just need a rest. It's commmon for these plants, the 'old-fashioned' varieties at least, to flower heavily for a year or two and then rest for a season. If you didn't have a late frost that would damage the forming buds, I suspect that's the answer. If the problem continues, you'll need to see if they're getting as much light as they used to.