What are the other conditions of the nuc? By your post I assume it is not growing...
Correct, it is dwindling.
Can you post pictures? You say no eggs, do you have problems spotting eggs? Have you ever spotted eggs in a hive before? If you perhaps have vision problems, have you looked with a small LED light?...
I can't spot eggs through a veil, so I usually take pics which I can then examine at high-res at my leisure.
Are the new cells on a frame of brood you added July 1st?
Are the queen cells capped. If so you are were queenless on July 1st and you are on less than day 13 (depending when the egg was laid in the cell) of the 28 day queen cycle again, from hatching to laying.
The nuc was started with a capped queen cell. Twenty days later, there was a new capped queen cell. At the last examination, there were two uncapped queen cells with larvae in them.