My pet finch is acting weird, what to do?

Lately my girl finch has been getting quiet, she is usually the loudest of all my other birds. I have 3 finches, I have 2 females, 1 male, african grey, parrolet. I don't my finches mated or anything because I don't have a nest box in their cage. :( What do I do? Do I put a nest box in there just in case? I really don't want any more finches. (it's not mating season is it?) Is my finch dying?