No, it does not look like mold it comes from salt building up in the bottom of the pot, which means a flush wouldn't be a bad idea if it's visible on the outside there's quite a bit in the pot.
I have it all the time,never caused any problem.Some say it is salt buildup,some say mold.I find it to be from my tap water and synthetic feeding.But there is nothing to worry about.Even if I'm wrong and it is mmold, it is definitely harmless
@DoctorGreenThumb You are right on. The airflow is not so good around the bottom. I will run the fan on it. Will it kill my plant????? cAN i FIX IT????