Hotend Won't Hold temp w/ fan above 55%

I am running filkemp (filament express) PLA. I quite like it. I extrude at 250c/ & 70mm/s (which sounds hot for PLA, but this is a special blend and they reccomend that temp at 70mm/s). I have a .5mm nozzle and am extruding at .61mm.

My issue is that if I run the fan at anything over 55% the hotend starts to cool off - down into the 230s.

Is this to be expected? Is it possible that this filament is a real ‘heatsink’ and that the volume I am pusing through at this speed is just too much cooling for the hotend to handle? Or, do I have a problem?

Thank you!!

So -

I may have solved it. The tip of my fan shroud was broken off by an inadvertant crash due to some bad gcode. I think the cooling fan was blowing air too high up on the hotend. I printed a new shroud.