Any idea what this is?

I have noticed this weird thing only in this leaf which is dying, the other leaves looks really healthy.
I purchased this orchid less than a month ago so I don't have many info. The leaf was already decaying when I got it and now these small round dots came out. I can't really understand if these are small snails.

 

Thanks for the reply. Here is the best I can take, I hope it is more clear