Baby Basil and Lemon Balm Plants Not Growing

Recently, I started growing two herbs on my windowsill; basil and lemon balm. They are about an inch or so high with almost their second set of leaves. The problem is that they have been stuck in this stage for almost 2 weeks. The lemon's leaves are starting to get yellow spots and the basil is just not growing. They get approximately 4 hours of full, direct sunlight and the rest of the day is bright but without direct sun. Why would they have stopped growing? Lack of direct sunlight? (I live in Maine, USA, so it's rather gray this time of the year.)

It could certainly be lack of sunlight if the 4 hours of sunlight per day are a rare occurrence. However, lemon balm can grow in sun or open shade and should therefore not mind the grey days.
It could be temperatures that are too low. Basil must have warmth and lots of light to grow well. Often a windowsill is much cooler than the rest of the house, but on sunny days the warming sun makes up for it and plant growth is not checked. Make sure that the soil in the pot is moist but not soggy wet and fertilize with an organic fertilizer if you have used a seed sowing soil mix. Such mixes are often poor in nutrients to discourage pathogens, but once the seeds are germinated they need more nutrients.