Good or Bad Nudibranch?

[SFJ]

I found some nudis while dipping my corals. I think these are Lettus Nudibranchs but I’m not sure. I just want to know if they are good or bad.

 

[sfin52]

I found some nudis while dipping my corals. I think these are Lettus Nudibranchs but I’m not sure. I just want to know if they are good or bad.
View attachment 2463420

What did you find them on?

 

[SFJ]

Two came from a rock with mushrooms on it the other was on the bottom of a frag plug with zoas on it. But I’ve never actually seen it in the tank. I was dipping for Red planaria