micro 30x30 grow RQS Bluematic

A week after I started the germination, the plant looks good and healthy (at least as far as I can tell :)). I started with a more proper watering with a root stimulator. In the middle of the week, several small spots appeared on the leaves. My guess was too much of nutes, since the royalmix substrate ca be a little too hot for the young plant. I gave it a small flush with power roots nutes only. If someone can tell, what it really is, let me know please :)