All pacts are mutually exclusive. Food logging only counts toward your food pact, veggie photos only count toward your veggie pact, and workouts only count toward your gym pact. There is no crossover credit.
Additionally, there is no crossover for pact charges/rewards. Food pact users who fall short of their pact will pay only the food pact users who made their pact. Gym pact users who miss their pact will only pay gym pact users, not food/veggie users.