Degu Owners

I've recently found this NG, and many of the Degu posts seem to be
dated. I have 2 female degus (sisters) and have for almost 3 years.
Their names are Aurora and Pandora (pandora is shy and hides in her
nesting box, or 'Pandora's Box')

I've been having issues recently with then chirping for no reason.
many times they would chirp if i forgot to feed them and they were
hungry, or if they needed a dust bath (used to give bi-weekly, now
weekly).

For any of you degu owners, have you had issues with random chirping?
i don't mean the adorable chittering they do when playing, i mean high
pitched, blood-curdling chirps they make the cats scared :) I was
thinking it mmay be their teeth bothering them, they chew on their
nesting box regularly and have a pumice stone. perhaps some wooden
perches or sticks to chew on?

any suggestions would be great, and i'll share my experiences as well!
You can see them on my myspace page, www.myspace.com/ltotheedbetter

Thanks!
Matthew L.