Leathers like this do this on a regular basis I believe for growth and to rid the outer layer of toxins and debris. They pout like this too if anything is "off" in the tank. Usually nothing to worry about and they will pout for a few days then shed their outer skin and be back to normal.
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45 Gallon Cube with 10 Gallon Sump, Lighting 8 bulb T5, Vertex IN 80 Skimmer
-2 Occelaris Clowns, Engineer Goby, RBTA, Peppermint Shrimp