I actually don't know what it is. 
It's Rafa mate. C'mon even you have to see it now, it's blindingly obvious. How can a team that was only 4 pts off the top last year, scored the most, had the highest goal difference and played several decent teams off the park all of a sudden turn into a side who struggle to eek out results against the worst of teams and have an abysmal away record?
Rafa didn't inherit this squad. If he did he may, just may, get some respite. He built his squad, took them as high as they could go (performance wise) last season and now they're on the way back down again.
I honestly think you just need a fresh start.