Most of the KDF Medics from the reinforcement doff packs with the bonus for "improve crew regen rate by +xxx% when your crew drops below 75% in combat" are bugged.
You can't apply them to your active space Doff's. They have the space bonus, but you can only add them to your active ground doffs (which obviously does no good). This has been a bug for some time now and doesn't seem to be getting better. I've submitted bug reports on this in the past. Please look into this.