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

We bought & planted 2 hydrangea PGs about 4 feet apart about one 1/2 weeks ago. They were both planted with the same fertilizer & get the same sun (morning) & shade (afternoon), but one is growing perfectly & the other has areas where all the leaves on a stalk are turning brown, even though there are flower heads on the stalk (but more heads are turning brown on this bush than on the other one). I was told to scrape a tiny section w/my fingernail & see if the stalk is green underneath (meaning the plant is still alive. I did this in a few spots having the brown leaves & all the stalks were green underneath. I have no experience with this bush, so I will welcome advice.

Generally speaking, you're NOT supposed to use weed killer in the same beds as good plants, because rain or watering can start washing it into the soil/roots around the good plants, and sicken or kill them from the ground up. I'd stick to hand-weeding and mulch for weed control IN beds. Or you can get some kind of slow-release fertilizer / weed controller pellets and apply that early in the season. Or at least consider gravity. If you water downhill from good plants you should be relatively okay. But if your plants are on the same level or downhill from the weed killer, there will be problems. Otherwise, your pictures indicate regular heat/sun stress behavior. This is normal, unless you water a little in the evening and the plant still looks like that first thing the next day.