Slow Growth

Hi Riu, just a quick question.

My month old seedlings are still exactly that, seedlings. The have only managed to grow 4 leaves in total the two seedling leaves, and two serated ones. They are outside, and we had had a bit of rain, but the soil ph is fine and i haven't fed them because of the rain, and they get minimum 10 hrs of direct sunlight a day - and another 5 or so hrs of indirect sunlight. What could be causing the slow growth?

What is the size of the pots you put them in?
What is the temp outside?
If they're in small pots it is very possible that the pots were getting really hot due to high temps outside and direct sunlight and hot roots = slow growth.