Challenge: Save my Hydrangea’s

I was a little late in planting two Hydrangea’s East facing. First time Hydrangea grower. This heat is testing my watering abilities. If we have another 3 months of this heat, how can I do to keep them alive? They have afternoon shade and lots of morning and midday sun. Soil pH is a little higher than I want, but it’s coming down with treatment. Any recommended fertiliser? Transplant shock due to the temps and late planting. Any other problems to be aware of? What are your preferred watering schedules?