Can you have too many ad networks in your app?

Just an honest question… 

I have an outside LUA file that successfully calls up a random ad from either Vungle, Playhaven, Chartboost, or AppNext. Do you think that is too much? Isn’t having all four somewhat counterproductive? The main reason I ask is because I’m seeing pretty dismal revenue numbers from each ad network. Granted, I only have 300 or so measly installs in the week my first Corona app’s been out, but still  :wink:

Is it better to just focus on one or two? BTW, I don’t use banner ads, only interstitials.