We live in south Louisiana, we have 6 bougainvillea plants on our patio that have missing flowers with the stems yellow and striped clean. We don't see snails or caterpillars in or around the area. I've included pictures below. Any idea as to what is the issue?

They may be root bound. Bougainvillea's grow very big and the container you have them on is too small. They would do best in the ground.