Your hydrangeas look healthy but I suspect the flower buds were killed by a late frost. I suggest you try the Endless Summer hydrangeas as these flower on both old and new wood. Do not prune your hydrangeas again this year and cover the plants with a sheet if cold weather is predicted after the month of March. You can also try the more cold hardy Invincibelle or mountain hydrangeas that can handle cold weather without losing their flower buds. As for the dahlias, I suggest you store the potted plants in a protected area like a garage or shed over the winter. Then in May dig up the tubers and plant them into the ground. They will flower the same summer. Keep growing, Marianne Binetti