Harry,
They look pretty good to me. The holes you are seeing are naturally occuring pits on the face of the discus. Yours for the most part are not something to be too worried about at this point, but often they indicate water quality issues or possibly mineral deficiencies when they start to enlarge. I see you do 80% 2x a week. I would try upping the frequency. Also measure your nitrates just before your water change. You mentioned a value of 10 for nitrates, but honestly thats not too likely with 80 % water changes every couple of days in a moderately stocked tank unless you have it well planted.
hth,
al