Did you actually take a rectal reading? What was it? Pupils dilated? The puppies being 4 weeks old is a common time for the Mom to develop low calcium. She probably needs to go to the vet first thing a.m., and get her calcium level checked and get a calcium injection - this could be very serious - you cannot simply give calcium to improve the level quickly. You might even have some emergency plans for tonight in case she gets worse.
here's a link on eclampsia - low calcium
http://www.lowchensaustralia.com/breeding/eclampsia.htm