Hydrangeas require some sunlight (morning or late afternoon, often referred to as "soft" sunlight), to bloom well. The macrophyllas (yours) also require an even applicaton of moisture during their active growing season. It is generally agreed, that the requirement is about 25mm (1 inch) per week. Those grown in containers will require more, due to the small soil mass and more rapid evaporation. With higher ambient temperatures, more evaporation will occur through the foliage (to keep it cool) and moisture requirements will escalate. Fertilization and frequency varies with location. In your area, addition of a slow release, balanced fertilizer can be applied twice each year, early spring and late summer. Rooted cuttings can benefit from a formula with extra phosphorus. I use a water soluble, 15-30-15, type during the first year of growth and after that, only an annual application of compost and/or leaf mold on the root zone. Don't know about prices of chemical fertilizer in AU, but the worldwide demand, especially in China & Africa, with limited supply sources, has driven up the price in the US to a point that it is almost unaffordable. Thus, my attempts at organic gardening, both ornamental and vegetable! Rb

Couple of thoughts.......avoid any overhead watering. When you need to water, do so at the root zone and do so thoroughly. Excessive water on foliage can lead to fungal diseases and leaf spotting. Second, you may have over-amended. Soil conditions radically different from those the plant was grown in can lead to shock. Ideally, if amending is required, it should be done over the largest possible area, never just the planting hole. And never a good idea to fertilize immediately on planting - the plant can't metabolize it. The good news is there is nothing wrong with your plants. The purple-brown coloration is just a reaction to cold, common to many plants, especially if not acclimated to the area or with more foliage than established inground plants may have. The spotting may be just a touch of leaf spot but nothing to get concerned about. Just change your watering methods and pray for warmer weather :-))

It is a powdery mildew infestation. Common in hydrangeas. I have even seen some at plant nurseries when they pack the pots closely to take less time when watering. To get rid of the fungus, make life miserable to the fungal spores by following some clean housekeeping guidelines: do not overhead water the shrub; instead, water the soil early in the mornings; throw away the spent flowers and leaves into the trash; discard plant debris under the shrub; replace the mulch with new mulch if the infestation is heavy; do not overwater as this increases the humidity in the environment and the spores will love you for that; separate plants to improve the air flow between them; consider fungicides if this problems occurs early (as it is doing now) and has spread a lot. First fungicide to try is milk: spray weekly during the day using 1 part milk to 9 parts water or slightly more concentrated. Because it works more to prevent PM, I sometimes use 4 teaspoons of baking soda, 2 tablespoons of horticultural oil and 1 gallon of water instead. If you decide to apply chemical fungicides, be aware that some can cost $$. Apply them on the top/bottom of the leaves per label directions. Consider reapplying next year before the time that this issue started (early May?). Fungicides Cleared for the Control of Powdery Mildew on Hydrangea: azoxystrobin (Heritage; has the smallest application rate and largest repeat interval); fenarimol (Rubigan); fenarimol (Cleary's 3336). You can also use Sunspray Ultrafine Oil. Luis

With the intensity of a midwest summer, I'd say a full sun location for this plant is just a bit too severe. The brown leaves are sunburn/scorch. It is a woodland plant in its native habitat and a full sun exposure without copious amounts of water is expecting a bit much of it. It is best sited on an eastern or northern exposure in rich, well-draining but moisture retentive soil. Unless located in very heavy shade, you can expect reliable blooming once it is well enough established, which can take a number of years. Personally, I'd relocate it to a shadier location (morning sun, afternoon shade preferred) or provide some sort of protection until your shade fills in.