That looks like not quite the right watering technique to me. It's not that easy with coco. The pots aren't able to let air reach the coco from the sides. For your next grow: use fabric pots, it's much easier to handle coco in them. If I look closer, I also see perlite... which coco do you have? If you mixed it yourself, did you rinse the coco fibers well before using them?