What it's this ?

Yes you’ve got pests. That is a sign of thrips with the leaf damage. Flip the leaf over and look with a magnifier or zoom. You’ll see movement. Does not look severe but it is something you should get a handle on now. Lady bugs, DE, or nematodes can help. Don’t use them in conjunction though. Glad to give your more detail on either if ya need it. I recommend every grow has an IPM protocol in place as a preventative measure...pests are part of nature and any “good” soil will attract pests. Part of the gam4. Good luck

It is nothing to worry about. Your plant will never have 100% perfect leaves, 100% of the time. Just like some people have "freckles", some plants will get tiny spots on their leaves for no reason at all. Also, without much more info/a diary, it is hard to tell if there is anything else that would cause it. I assume you can rule out insects? Either way, it doesn't really matter, the leaves are OK, and your plants look fine to me. Good luck and happy growing!