Just my 2 cents.

I think you keep them under direct afternoon sunlight. First of all, older pbulb might not plump up again.

Although cattleya are known for light loving orchids , still vary the amount sunlight they can take from species to species, one plant to one plant especially under afternoon direct sunlight. Thus why, there are upper & lower light level for this genus for successful growing. Seasonal sunlight changes also have to be taken into consideration. Summer sunlight is much stronger and you may need protection & keep humidity high.. Generally, afternoon directly sunlight is strong for them.

I would assume your potting mix still is not degraded. If degraded, repot in fresh medium. Don't use too big pot. Just comfortably enough the root ball to fit in.

Also little or no roots when the plant was actively growing could be a reason. In such case, the plant cannot absorb water due to root loss/less roots no matter how you water it.

One tip for watering plant in bark mix is soak the entire plant in a small tub for about half an hour /one hour. This will help bark medium thoroughly saturated.

Sometimes, it needs time to acclimatize the place where you put your plant. If suddenly expose to strong sunlight, it may easily get sunburn & shocked. You can keep under shade cloth/net to prevent this.

During plant growth phase, you may need to water more often also. Don't wait till too dry during this phase, it may result in stunt growth.

Another point I think is humidity. Keeping plants together will increase humidity. How many cattleya you are keeping together? Having foliage plant or watering/wetting the floor will also increase humidity. Plants tend to plump too.

In my humble opinion, keep your plant under direct sunlight with shade net while maintaining high humidity.

Keeping them under optimal sunlight couple with adequate watering will definitely give you beautiful leave & blooms.

Happy growing.