Apistogramma Cacatuoides Problems; What Should I Do?

[Channti]

I started out with three Apistogramma Cacatuoides; a fish I rarely see in my area.  Two females, one male, and things went great for a good six months.  Over Christmas, my male passed away while I was away for a few days, cause of death unknown (tank conditions were right where they should have been).  Over the last month, I've watched the health of my second female turn awful.
 
While one female had always been slightly larger than the other, the two are now completely disproportionate in size.  I'm fairly certain that the larger female has been bullying the smaller female into not eating at all.  The colour differences and size differences in them are shocking, with the larger showing beautiful colouring and healthy build, while the smaller is scrawny, and has really dark colouring all the time.
 
I've separated her (The smaller, scrawny female) into a guppy breeder net that I keep for making tank refills easier.  I'm debating on what my options are now.
 
Would it be acceptable to move the smaller female into a 5 gallon tank until I get some food into her, and then re-introduce her (hopefully with another female and a new male) in a month or so?.

 

[Sammy1911]

I didnt want to read and run so i think it sounds like it could be bacterial? or possible parasites? But beware cacs are known to "pretend" to be female to avoid aggression (you can google this) so the aggressive one you have could well be a male who is now making a territory for itself. i personally would split them in the effort of saving the "sick" one others may disagree though. i have found apistos very delicate even when i got them from private breeders but very beautiful when they're healthy! good luck, hope it all works.