Because the clogs are still there but the piezoflush has entered the head (aka, faint color), it means that both the dampers and the cleaning assembly are working. Because your clogs are not changing (at all?), it most-likely means that the nozzles in those areas had shorted out when they were appearing clogged in the first place. This is common to all x900 heads.
One never wants to actually print [I]anything[/I] when nozzle clogs are happening because that is actually what shorts them. At this point it is probably confirmed that your head has burned nozzles.
The way these nozzles go is gradually (most often). You will have one stubborn clog and then it will widen around the surrounding nozzles. The one thing you can attempt at this point (last ditch effort) is to do a SSCL cleaning from the maintenance mode (google it). This will fire the heads while sucking with the cleaning assembly vacuum. This is generally not recommended unless you are pretty sure the head is toast. If you see a change in even two or three nozzles, this may mean a failure of the damper assembly filters that let particulate and air into the head inlets. (I doubt it).
regards and sorry for the bad news,
R&D (and wrestler of x900s) IJM