Leaves that stay wilted constantly can be caused by bad weather -like a late frost- or by a watering issue or root rot.
Bad weather (frost) usually develops after the plants break dormancy too early (for you, the average date of last frost is the 1st or 2nd week in May) so maintain them well mulched with 2-4" of mulch. Water deeply the night before frosts. Cover them with frost cloth if it will have a little dip below freezing or, in the case of hydrangeas that bloom on old wood, give them winter protection in the Fall and remove it about two weeks after your average date of last frost. Roots are usually not bothered by frost as the ground insulates them but leaves and stems can get zapped. It looks like yours leaves may have gotten a partial hit as they have not browned out. The frost on the 25th may have caused the problem.
If they are not getting enough water, the leaves will also wilt but they should perk up when the soil moisture is restored when you water them. It is best to keep the soil as evenly moist as you can, with no times of dry soil followed by wet soil, followed by dry soil again.
If the leaves remain wilted 24/7, they could also be suffering from root rot from overwatering. This one is hard to differentiate from damage caused by weather. One would have to extract the plant and inspect the leaves to see if they are rotted or smelly.
Wait to fertilize until two weeks after your average date of last frost. Ferts will put the plants officially in "grow mode" so it is always very "inconvenient" when late frosts happen.
You can use a general purpose, slow release, chemical fertilizer with a NPK Ratio of around 10-10-10; or you can apply 1/2 to 1 cup of cottonseed meal, organic compost or composted manure only once in Spring. That should do it for whole year. Once they become established, do not fertilize any more. Let them feed off the decomposing organic mulch. Hydrangeas are not hungry plants like roses so they will be fine if you maintain them mulched all year around. Some formulations of Miracid can have high nitrogen levels like 30-10-10 so look for something close to 10-10-10.
So for now, do nothing but keep the soil moist. Insert a finger into the soil to a depth of 4". If it feels dry or almost dry, then water. The amount of water per watering will vary. Start with one gallon and see if that gets the soil moist or wet; after the watering, a finger should feel the soil moist or wet to a depth of 8". Water only the soil (never the leaves) early in the morning. Start from the root ball and water in all directions outwards.
