Well, none were upgraded to C/Ds - but then the C/D (unlike the F-35 Block 3F) was developed to deliver capabilities not in the original contract. Also, many Block 1 and Block 5 aircraft were upgraded to Block 10s and at least some Block 10s made it all the way to MLU, which was superior to the initial C/D.
And you might ask the Iraqis whether or not the Block 10 was a fully combat capable aircraft.