NO! Relay fault usually means lamps either don't come on at all, or come on and don't flash. Have you checked/changed the bulb in the one not coming on? Try a new bulb first, and check the bulb holder is clean and not rusty, and also the little stud thingy that contacts the bottom of the bulb is clean, if in doubt, give it a gentle scrape with a screwdriver to make sure it is clean. If a new bulb/cleaning doesn't cure it, it's time to check the earth and wiring to the indicator in question.