Nazgul At Pelennor

[Eurytus]

Yes, the attacks were simultaneous (the battle in the Pelennor fields and the attacks to Lorien). And there is no explicit mention that any of the Nazgûl were in that battle (in the Pelennor) with the expception of the Witch King.

In my previous post when I stated that the attacks on Lorien happened simultaneous with the events in Gondor I meant all the events, including the march to the Black Gate.
Given that at various times the Nazgul were watching over the Pellenor Fields and were spying on the army as it approached the Black Gate, and later were all there above the Black Gate I think it safe to say that it is unlikely that they would have been at Dul Guldor.