Bro, don't panic yet. I'm no Nudi expert, so I may be wrong.
From what I read, Nudis usually have specific diet and may only go for 1 type of food. Like only sponge, zoas, SPS, algae or others.
So first of all is to find out what Nudis you have, while you continue to manually remove what you can.
Once you establish what type they are, then take more widespread corrective actions, if needed.
Hey, for all you know, maybe you have the Lettuce Nudi which are algae eaters.