Flower drop, leaf curling, and yellowing may be caused by several things. Since water levels and fertilizer are good, and it doesn't seem that your area is getting high heat (over 90F) or really cold nights, then best guess would be the tarnished plant bug, which sucks juices from plant buds and can lead to blossom drop. Thrips or aphids might also be culprits. As to diseases, check for wilts and viruses, especially verticillium wilt.
Flower drop, leaf curling, and yellowing may be caused by several things. Since water levels and fertilizer are good, and it doesn't seem that your area is getting high heat (over 90F) or really cold nights, then best guess would be the tarnished plant bug, which sucks juices from plant buds and can lead to blossom drop. Thrips or aphids might also be culprits. As to diseases, check for wilts and viruses, especially verticillium wilt.
For more information about pepper problems, see:
http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG57_IPM_Series_Peppers.pdf
and about tarnished plant bug:
http://entnemdept.ufl.edu/creatures/trees/tarnished_plant_bug.htm
http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/plant-bugs/tarnished-and-four-lined-plant-bugs.aspx