New leaf growth problem
 

Some, but not all of my catts, create new growths whose leaves do not expand and open up and their pseudo bulbs do not thicken. The new unfurled leaf looks like a knife blade. Yet other catts do not have this problem. Does anyone know what is going on that would please:( help me understand?

This can happen when humidity is way too low, or when you don't water enough.

Thanks for your advice. That makes two of you who have given the same advice. In the beginning years I watered too much as many of us did. Now I think I'm under watering. But I repotted or threw away several catts yesterday and their oldest roots were all rotten. I suppose they were from the over-watering in recent past two years. But the few newest roots were okay, so I sprayed them with fungicide and repotted into smaller pots. It will take a couple of years to reach flowering again but at least I saved them. Thanks again for your advice!

Cattleyas make roots only on the newest growths. Older pseudobulb's roots mostly serve to anchor the plant. A lot of people divide leaving about 4 growths total. The back bulb division often makes new growth if treated well. It's fine to cut off slimy dead roots, but often dried brown roots still have some functionality.

My initial question was about the newest vegetative growths not unfurling and remaining in the shape of a knife blade. But thank you for reminding me that new roots only grow from the newest growths. That makes me feel better.