I purchased a tibouchina last year from a local nursery here in Puerto Vallarta, Mexico. It did not do well and had problems with die-back of entire branches at times. I took cuttings from healthy looking branches and am now trying to grow them on into larger plants. Initially the cuttings thrived. However, I've noticed recently that terminal shoots develop, but the new leaves on those shoots fall off before developing, leaving bare "twigs". Is this a fungal or bacterial disease inherited from the mother plant that I have since discarded; or, is it indicative of an insect pest? Thanks for any help.