Blooms should typically go through a series of changes such as they start pink; colors fade; blooms turn pink; blooms add pink/burgundy splotches; blooms turn a shade of brown. Premature browning of the blooms suggests that any of these stressor events occurred by itself or in any combination: direct sun after 11am; lack of soil moisture; lack of enough soil moisture; very windy conditions; root disturbance/damage due to recent transplanting/underground pests/etc.; or excessively high temperatures with low humidity that desiccated the blooms.. If the stressor event lasts long enough, the leaves will lose moisture as well and start to brown out from the edges inwards. Maintain the soil always damp/moist during the summer months. Use 3-4" of mulch past the drip line. Ensure that the plants get morning sun only and that you use enough water to moisten the soil down to a depth of about 8" or so. Hydrangeas planted in the middle of the summer months tend to be very sensitive to heat, especially if they are not slowly acclimated to the outside conditions when brought home from the plant nursery, where they are coddled in little sun or even just bright shade.

bonemeal, mulch, and once a year check the soil, mix it up, decent drainage, make sure roots are healthy. morning sun, lightly shaded/not direct sun for the remaining day. pruning to ground level can help them, but only in certain seasons. too much nitrogen can cause damage too.