[paladinbaby]

I have a 10 gallon tank, heated, filtered. PWC and filter changes monthly, with 3 betas in it. one male, Blue, separated by a plastic mesh divider (he was labeled female but is much too flirty and aggressive to be so), then 2 females, Luna and Shadow. This has been the set-up for over a year maybe 18 months+

These past few days Shadow has been becoming more and more emaciated but is acting completely normal. Still playing with Luna, eating like a little pig, and flirting with Blue. I noticed something was wrong when she started losing a bit of her color and becoming kind of pale last wednesday but I was scheduled to be out of town for a few days and when I returned she was much worse, still acting normal though. I asked my mother to take care of them so I know they were fed.

My main issue right now is, I have lost enough fish to know when one is a goner. I'm going to separate shadow into her own bowl and keep her comfortable until the end, but I dont know if its internal parasite or fish tuberculosis and I dont have proper medication to treat either. I know that the others are as good as dead if its TB but what if its only parasites? What can I do to prevent Luna and Blue getting this too?

Thanks in advance for your help.