Hibiscus Blooms

[Lostinparadise]

I have a Tropical Hibiscus (orange) that was recently planted in my yard. It has been doing well and producing blooms; however, today a few buds dropped before opening and the one that did open today appears sickly. The color is dull and there are grey/white areas on the petal that kinda look like water residue, but I can't tell. The leaves appear fine - no sign of pests or yellowing - but I did notice a couple pinholes on today's bloom. The plant is in full sun and the temperature is about 82 F today and was that or less yesterday. Would this be caused by over or under watering?