Darn Powerhead ?!?!?

[BubBleBee]

Came home this noon to find a danio and pea puffer belly up...did a water test and everything cool in that department! Started to put snails into the tank for the puffers and I noticed another one of my danio's plastered to the power head... struggling to breath...got a net and gently pulled it away...as I'm doin a count of my tetra's....(coming up short) noticed one stuck in one of the grooves in the power head dead......wondering why this is happening?? The power head is an Aqueon 700 which has been in that tank for 3 days and all of a sudden today 3 casualties!! My tank is a 46 Bow if that matters any. Any input would be greatly appreciated. I have turned it off don't wanna lose anymore of my fish....:'(