It looks like the biggest problem is your lack of sufficient sunlight - would explain why they have stretched so much with little branching; they are trying to get to some sunlight. I'd advise you to transplant them into a better location with better lighting. When you transplanted you could then provide them good, fresh soil with nutrients. I would also mix in about 30-40% perllite, to allow your roots to grow better/faster. If you're using MG soil, I wouldn't put much in the way of nutrients - maybe a bit of Superthrive to encourage root development.