So I planted two mint seedlings about 3 weeks ago, they are in the same pot around 30cm apart, and were doing fine up until about a few days ago. I have noticed that the leaves around the bottom of the plant have started to turn yellow and aren't growing any bigger, and the leaves around the tops of the plants have started to go a little brown, with some getting holes in them. I'm not sure what to do with them now. Since planting them I haven't put any fertilisers on them or anything like that, I've just been watering them almost everyday and leaving them alone in their pot in our front yard.