I'm not sure because I only speak for cloudminers.net, but I think these are individual issues.
I launched the pool 6 hours after the coin was released, at that time the diff was already 40 ish.
I only got 30MH pointed to the pool while the diff of the coin raised.
We are at +/- 50% of finding a block, so in short we need more hash pointed to our pool in order to find blocks.
Supernova currently has over 1GH pointed to their pool, so thats why they are finding blocks.