No, they are particles of synthetic fabric and I checked in the photo of the cover is clearly seen, and already remove that material was on the terrace near something near the plants, I usually have the clinical eye and when I have doubts, investigate, so I took an eye all over the terrace, even came to think it was cat hair but no, it is what I mentioned.
I also helped myself with a magnifying glass to remove debris that was on the leaves, but in the morning if the weather is still good I will keep checking.