sorry you have been waiting a while .
just to confirm the part you are describing are they the copper washers that sit at the bas of the injector?
Yes that is correct, diesel seepage has buildup carbon on the seat and the copper gasket has remained firmly on the seat
sorry you have had to wait for a reply there is a big time difference so i hope i am not too late to offer you some help.
firstly i would deposit some wd40 or similar just a small amount down the tubes.
secondly with a long falt blade screwdriver wide enough to overlap the injetor tip hole
plce on top of the copper washer and gently tap with a hammer being carefull not to go through the copper and damage the seat.
then try to turn the washer.
with a smaller blade screwdriver with a dollop of grease on the end retrieve the washer.
let me know how it goes.