Try to check your hot end for a partial blockage. I usually do this by heating the hotend and then inserting a thin metal wire (from a metallic brush for instance) into the tip (from below). Take precautions.

It could be due to increased friction on the filament path but improbable.

OR, would you somehow have modified (by mistake ?) your flow rate parameter ?

edit : is it the same filament ? If not, is the diameter within acceptable range of the spec ?