female husky siblings 6 years sudden fighting

Question
My two female huskies (sisters) aged 6 years suddenly started fighting at night (not in the day) after i had been on vacation for 1 week.  only food treats will stop this behaviour (which obviously compounds the problem).  need some advice on a safe method to stop them/separate them when in  a fight (citronella spray not effective) and some advice on what to do long term.  Desperate as 6 weeks now and if not change will have to get rid of one or both.  

Answer
Crate them up at night, or kennel them seperatly in other rooms.
Here is an artical about crate training an older dog.
http://www.k9web.com/dog-faqs/new-dog.html#crate_training

You will have to do this to both of them or the one that is loose will start thinking to much of themselves and will make the problem worse. Try to stay with them during the day. Using traeats to break up the problem isn't a bad idea, if you don't use it all the time. That way fight doesn't = treat. The only way to safly break up a fight among bitches is using a cair to get between them and shout at them whey you have their attention.

Here is an artical and it includes a video on how to break up a fight safely.
http://leerburg.com/dogfight.htm

If you have anymore questions please ask!
-Michelle B