What did you do with the soil before planting? I always test the soil and do ;lots of adding compost, peat moss or sometimes sand depending on my soil . Some plants do not like cedar mulch. The best is to go to your garden center and ask this question Sometimes buying a plant that is close to flowering just needs another season to get established .

New hydrangeas are normally kept in part shade and coddled considerably by the wholesaler and the local plant nurseries. When brought outside and planted in full sun in the middle of summer, the blooms may brown out early until the plant becomes established in the garden and develops a large root system. Normally though, the blooms will go through a series of color changes and if you observe that they are turning brown "early", I would start to monitor the amount of sunlight and the amount of water that they receive. In their first year, I have been known to provide temporary shade in the form of outside chairs and even built some cardboard contraptions. To monitor the water, insert a finger into the soil to a depth of 4" and water if the soil feels dry or almost dry. The amount of water used should be enough to get the soil moist down to a depth of 8". Use 2-4" of organic mulch at all times of the year. The spent blooms can be deadhead now or you can keep them for winter interest. Otherwise, the plant looks fine. The other plant that you have may be older, may have more shade or may have a larger root system. In the extreme south, paniculatas like Bobo tend to bloom just as temperatures spike to the 100's and that can brown out blooms too.