notaspidea's Identifications

Although no rhinophore papillae are present, I think it might still be this species. Both are very small.
I saw the larger individual within the athecate hydroids on a floating M. pyrifera at the beach which is why I took a few blades up to my aquarium. Not knowing there were multiple other nudibranchs on them as well.

~4 and 2 mm long.

Edit: Added image 4, no sign of white foot margin line or papillae. Size is ~5 mm