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.

[NYCorchidman]

For that particular plant, you should go on doing what you've been doing because apparently you've been giving it the right culture.

Just make sure the buds are not touching the bulbs as they grow bigger.

Many cattleyas are seasonal bloomers, and day/night length is the cue they use in deciding what season they are in.

Some hybrids may bloom off of every new lead, but many are seasonal.

You just have to learn as you go.
That is why you want to grow in the natural light or change the light hours according to the season to find out which cattleyas bloom when.