Pro mix is not the best medium to grow in , I wanted to use it with Kind soil but kind did not recommend it do to its contents, so I went with happy frog. that being said the seedling look ok maybe the spots are from the light, from the picture of the grow space they look to be about 16 to 18 inches from light but that is a strong light, my suggestion is leave them in the cups for about two weeks this gives the roots a chance to grow out to sides then transplant so there forever home. the spots could be caused by alot of thing so its really hard to give good answers with the info you have provided, the spots are not normal but they may be easily fixed. except for autos I grow in coco/perlite mix this enables me to give exactly what I want them to have