I just bought a bougainvilla plant, & it was flowering beautifully. However, it has since dropped its' flowers & shows no sign of re-blooming. I've checked it for insects & there seems to be no sign. It get plenty of light, & I am a container gardener. How do I get it to re-bloom? Any help will be HUGELY appreciated, as this is my first bougainvilla. Thank you.