The filament extruding from my extruder+ on our Makerbot mini is very thin. Why might this be?
I have cleared filament traces from within the extruder and the filament is makerbots own PLA.

Try a new nozzle, they get clogged and the only fix is to just replace it after a while.

Try Settings > Move Axis > Extruder to manually advance the filament for 10 seconds. Does the motor slow down while making a pile of string on the bed? If it reliably extrudes at the same rate for the 10 seconds, the problem is most likely not the extruder.