growing slowly

The 2 seedlings that seem to be a bit paler than the others look as though they are in a different soil mix. This mix looks cheap and nasty with plenty of wood chips, which means its nutritional levels will be low and this could be a reason for their poor performance. Also, there is not much soil in the pots, meaning they miss out on a lot of the reflected light by being so deep down inside the pots, another reason for slow growth. I would be carefully transplanting them into pots filled to the top with the best potting soil I could find, something designed for vegetable/herb growing. Quite simply, you can't grow good plants in cheap dirt!

The small rounded leaves that are going yellow are known as "cotyledons" They are not leaves in the true sense. Their only purpose is to protect the growing tip as it pushes its way through the soil on its way to the surface. After this they peel back to expose the first true leaves (the serrated ones) to the light and begin the cycle of life. They then turn yellow, die and fall off, as their function in life has been done. All this is natural and normal in the life of a cannabis plant and there is nothing that can be done to keep the cotyledons from going yellow, dying and falling off after a few days in the life of a cannabis plant. Your plant does not need any help at this stage, nothing will save the cotyledons! Hope this helps, Organoman.