Won't be surprised if it turns out those S5's you've deployed have a conflict of sorts with the pool .... they seem to have drawn all the luck outta slush!
Any chance you can elaborate on this?
I've been mining with Slushs for about a month or so now. I think its a brilliant pool although I must admit it can be rough when you go through a 20hr patch with no block found @ 10+phash pool speed.
Today was pretty sweet though, 5 blocks in a short time frame. Unfortunate all my power wasn't dedicated to the pool though!