Now you have plants I wouldn't bother. Yes, the bacteria won't increase in number, but that doesn't matter with plants. But if you are worried, add the one third dose of ammonia every 3 days - that's 0.8 ml every 3 days. Then do the big water change before fish shopping.
The bacteria are dying off and being 'born' all the time (bacteria are 'born' by one bacterium splitting into two).
When there's more food than the current number can eat, more are 'born' than die. This is the situation during fishless cycling, we add a lot of ammonia to get them to multiply faster than dying.
When there are fish in the tank, if the amount of fish stays the same, the amount of ammonia they make stays the same and the bacteria multiply and die off at the same rate so the total numbers of bacteria stay the same.
When there is less food, more die than are 'born' and the total numbers reduce to the amount of bacteria which can live on the lower amount of food, then they stabilise at a constant number.
Plants take up ammonia as fertiliser and they do it faster than the bacteria can. In a planted tank, the plants grab most of the food (ammonia) made by the fish, leaving only a bit for the bacteria. You have grown a lot a both types of bacteria, just that the nitrite ones at the moment are not quite enough to eat all the nitrite made from 3 ppm ammonia in 24 hours.
Now that you have plants, they will take up ammonia and once you have fish you'll be in the last of the scenarios above - there will be less food available for the bacteria than during cycling because the plants will take up some of the ammonia, and less ammonia for the ammonia eaters also means less nitrite being made. With live plants, you don't need as many bacteria as a tank with no live plants. The amount of bacteria you have grown will be more than are needed now you have plants. The bacteria you've grown won't all die at once if you don't add 3 ppm ammonia; they'll begin to reduce in number just because of the plants.
The reason you've been doing a fishless cycle is because you are new to plants and at the moment your plant keeping skills are an unknown quantity. Are you good enough at growing plants that you don't need any bacteria, or will you need some bacteria to remove ammonia if the plants don't grow well or aren't enough plants or the plants are all slow growers which don't need as much ammonia as fast growers? That's why you needed to have grown some bacteria before getting fish.
The bacteria are dying off and being 'born' all the time (bacteria are 'born' by one bacterium splitting into two).
When there's more food than the current number can eat, more are 'born' than die. This is the situation during fishless cycling, we add a lot of ammonia to get them to multiply faster than dying.
When there are fish in the tank, if the amount of fish stays the same, the amount of ammonia they make stays the same and the bacteria multiply and die off at the same rate so the total numbers of bacteria stay the same.
When there is less food, more die than are 'born' and the total numbers reduce to the amount of bacteria which can live on the lower amount of food, then they stabilise at a constant number.
Plants take up ammonia as fertiliser and they do it faster than the bacteria can. In a planted tank, the plants grab most of the food (ammonia) made by the fish, leaving only a bit for the bacteria. You have grown a lot a both types of bacteria, just that the nitrite ones at the moment are not quite enough to eat all the nitrite made from 3 ppm ammonia in 24 hours.
Now that you have plants, they will take up ammonia and once you have fish you'll be in the last of the scenarios above - there will be less food available for the bacteria than during cycling because the plants will take up some of the ammonia, and less ammonia for the ammonia eaters also means less nitrite being made. With live plants, you don't need as many bacteria as a tank with no live plants. The amount of bacteria you have grown will be more than are needed now you have plants. The bacteria you've grown won't all die at once if you don't add 3 ppm ammonia; they'll begin to reduce in number just because of the plants.
The reason you've been doing a fishless cycle is because you are new to plants and at the moment your plant keeping skills are an unknown quantity. Are you good enough at growing plants that you don't need any bacteria, or will you need some bacteria to remove ammonia if the plants don't grow well or aren't enough plants or the plants are all slow growers which don't need as much ammonia as fast growers? That's why you needed to have grown some bacteria before getting fish.