I would
not recommend using ammonia. Plants doing well was mentioned in the first post, so if you have plants you should not add ammonia. You risk harming the plants. Plus, the plants are taking up any ammonia present naturally, which is why you should see zero ammonia, zero nitrite and zero nitrate with your tests. Plants do what we call a "silent cycle," because the minimal ammonia that gets by them will establish the nitrifying bacteria but it will not be sufficient to show up in the tests. A photo of the tank would help us know they are sufficient. Faster-growing plants, esp floating plants, are ideal.
The pygmy cories must have a larger group. Twelve would be better, or a few more. I personally would be very watchful of the gudgeons with this tiny cory, they are very delicate.
And welcome to TFF.