Is it getting too much sun? I have read they like morning sun and afternoon shade.

They are in full sun until about 4:00 or 5:00 shade from then on. They are only a week and a half old.

It is getting too much sun. It looks to be a florist or grocery store mophead (Hydrangea macrophylla). It is a large leaf, under-story bush that does best in dappled sun conditions that are not windy; or in morning sun (till 11am-ish) and afternoon shade; or in full but bright shade (the indirect sunlight can bounce off walls or cement surfaces or sun that shines near but never strikes the plant). Florist hydrangeas sometimes have a hard time with sudden exposure to the sun and must be brought into the light slowly. For example: several days of full bright shade; then several days of 2-hrs long morning sun; then more morning sun. You can do this by covering it with a lounge chair for the outside and slowly get it used to the sun. About 3-4" of organic mulch and 1 gallon of water per watering also helps. Insert a finger to a depth of 4" into the soil close to the potting soil. Then water if the soil feels dry or almost dry. If the day is going to be windy, make sure the soil is moist, never wet unless it has recently rained or you have recently watered it. Providing water to blooms on the first year requires extra water too so consider cutting them off if the extra sun exposure made the blooms brown out. It produces invisible flower buds in July-August and these open in the following Spring. Consider winter protection if you are in cold zones. Will bloom more reliably too if you winter protect in the Fall. If you are in Zones 5 or colder, it may not do well and be an annual plant but it is hard to tell for sure as florist hydrangeas do not get identification by name in the plant label. The blue blooms may change in future years to other shades of blue, or purple or pink depending on whether your soil is acidic or alkaline and whether it has enough naturally occuring aluminum. Amending the soil with aluminum sulfate will help maintain blues in future years but apply per label directions as the soil will revert back to its original state if you stop amending.

Cannot improve on the above response. Just to confirm and agree that, if you want to buy a Hydrangea to plant out in the garden immediately (depending of course, on the time of year/weather conditions!) it's always best to buy from a reputable garden centre, where they are raised and kept outside in the garden section as a matter of course.

The plants from florists or even large supermarkets really do need acclimatising slowly....

Great response, Luis_pr.