Also - I do think it's very difficult to overdose on Prime, but there is a level at which too much Prime can start to affect the oxygen level in a pond. Based on the instructions, it doesn't appear you used too much though:
Prime for Ponds:Use 1/8 cup (2 tablespoons) for each 600-700 gallons for removing chlorine or chloramine. To detoxify high concentrations of ammonia or nitrite, use 1/4 to 1/2 cup for each 600 gallons. Sulfur odor is normal. For exceptionally high chloramine concentrations, a double dose may be used safely. To detoxify nitrite in an emergency, up to 5 times normal dose may be used. If temperature is > 30 °C (86 °F) and chlorine or ammonia levels are low, use a half dose.
However, Prime doesn't resolve the cause of the high ammonia - it only contains it long enough for you to correct the issue. In your case I would suspect an overstocked, immature pond, if indeed high ammonia was the culprit.