Thank you so much
@carolem !
I did contact the supplier as well, but they haven't responded.
The picture was actually found online - with the exact same color and spot patterns. I tried to take a few pictures myself, but my phone's camera isn't very good and the purple dots were barely visible. So I "stole" the picture instead since it's much clearer. The website listed the picture, didn't say anything other than "marigold seedling".
I have some marigold seeds sowed hydroponically as well - exact same symptoms.
The strange thing is the purple color is there as early as the first pair of leaves appeared, and the spots are so evenly distributed. Every single seedling has the same symptom.
It would be really very interesting if it's indeed just this particular variety.
