I'm not sure what that is but I've similar black spotting on roses that were infected with a type of mold. I'd avoid using outdoor soil for an indoor grow as outdoors soil will bring small bugs. Potting soil is sterilized at the factory and if bugs get to it, it's usually after you buy it and they get into the grow room. You can use outdoor soil if you want but it's less predictable. It's possible that the black spotting is a result of a deficiency; either that or it is a disease, not sure which. Since I don't know what that is, it's hard to tell you how to solve it.