Startapp CPM... low?

Hi guys, I’m new in the forums, first of all, hi to everybody!! I’m writing here because I need your opinions… I switched from Airpush to Startapp some days ago, everything went very good at first, but now, one or two weeks after, CPM went drastically low! This are my stats of today in 3 of my apps…

New Installs Interstitials CPM Earnings
1,195 10,288 $0.81 $ 10.43
413 6,950 $0.49 $ 4.54
393 3,184 $0.68 $ 3.13

Is this ok? I think it should be better, do you know any better ad network, (I use interstitials)

Thanks in advance!

it’s poor. I have only one application with startapp - it makes about 2 1.78 eCPM and most of my users are from Russia for this app.