BRDAV is getting older and has done strictly TV guest appearences the last few years.
CKILB felll off the face of the earth 3 years ago and has not been seen since.
SDOGG has an indie movie that has filmed [as described on The Bucket List]; hasnt been determined if it is STV (not going to be listed by HSX) or theater (will be listed by HSX when it has been decided)
SBUSH is a popular actress who has stuck with her TV show; it is not known whether her show will be getting renewed for next season. If not renewed, it is highly probable that she will jump back into movies quickly.
These are just my guesses why those 2 delisted and the other 2 didn't