Seems like some time ago, a lot of hashing power joined the network, mined a lot of coins, dumped some. The mining difficulty was raised, that hashing power left the network. The current hashing power is not enough to keep finding block every 10min. This should change when the difficulty is recalculated. That is just one unfortunate/ugly side effect of POW (proof of work) algorithm of securing the blockchain. Mining pools should scale  this problem down.