Catt's not blooming ever

[ginnyr]

I've had a couple of cattelayas for 3-4 years now and while one gave me a bloom once, the others have not produced a bloom ever. I have them in a South facing window and they get bright but indirect sun. At this point the largest definitely needs separating and repotting but the other 2 do not. All my orchids (I also have 3 phals which bloom almost continuously) are watered with a weak fertilizer solution and the Catts are watered only when they appear dry. That could be a week or even 10 days apart. Any suggestions as to how I can get the Catts to bloom?