I believe there currently is a shortage of CRJ crew. Apparently, people have been offered CRJ courses. Meanwhile, somebody who is rated on the CRJ is doing a course for the dash, which does not make sense to me.
I believe that people are leaving because they are fed up with FlyBE. Salaries are way below the average, no payrise whatsoever - not even inflation - for years, frozen duty pay, no real career progression, etc.
These issues will have to be addressed soon.
If the company are changing the ration of TP versus JETs in favour of the turboprops, I reckon many people will leave simply because they are stuck on the dash without any real prospects of getting on a jet in the forseeable future.