This may possibly be flukes. One way to eliminate them or the possibility is to give both of them a freshwater dip in the same temperature as the display tank for about 5 minutes. Thereafter, return fish to display.
Look then on the bottom of container you used for the dip for what looks like sesame seeds or fish scales. If you can see that- Flukes. If not, you will need to begin quarantine for parasite and recommended would be coppersafe. Dose coppersafe according to package but also at 85% of recommended to compensate for useable gallons.