Definitely do not add more fish. Are you doing a lot of partial water changes? You should, even at .5 the ammonia is stressing the fish, and if they're not hardy fish they could get sick very quickly.
The more fish you add, the higher the ammonia will be because of the excess fish waste, and your media (filter, bacteria etc.) is not strong/mature enough to withstand combating it at only 14 days. You're looking at a minimum of a month in my experience for a stable environment/cycled tank, with or without fish mixed in with the cycling process. But keep in mind, with such a young tank, you're going to have ammonia spikes every time you add a new guy until your filter media is strong, even after the tank is "originally" cycled
check that ammonia often, do daily partial water changes, because it can spike in an instant and you could have sick critters in no time