Plural of "medium" as a fine art term...

If someone paints using more than one medium (say, oils and pastels) would a descriptive sentence say "Atrist A uses serveral media" or "Artist A uses several mediums". In the first sentence I feel like she's sounding "multi-media" (which is nothing to do with art materials) whereas in the second, she sounds like she's using a lot of psychics!

Your help would be very much appreciated!