After 12 days from start mixing and two circles run, my Tetenal E6 First Dev is showing a lot of floating "grain" (sorry I dont know a proper word). So is it still working or it's dead now?
Yes, E6 FD does this. I have no idea what this stuff is, and I never put in much effort to find out, because E6 FD with this precipitate works just as well in my experience.
Even if he didn't (Tetenal FD has a sequestering agent after all AFAIK), the amount of precipitate is much higher than what could be possibly dissolved in tap water.