Empty sheath?

[Leafmite]

I hope someone else will help you as I don't have experience growing under lights. I know that is very different from growing inside with natural lighting. I have mostly seedling cattleyas and the ones that do bloom for me, bloom without any special treatment. Right now, I have one that is just pushing sheaths but it won't bloom until about April. I have another cattleya that doesn't use sheaths at all...the buds just appear and then it blooms. Cattleyas are very different depending on their genetics.