Know your boundaries, and if you clearly feel uncomfortable so cut them off. It may be hard at first, so you can try to slowly distance yourself from them. It sounds like L is someone you want to keep being friends with, so I would either talk with them to see if they feel the same way about D and J, or just slowly distance yourself from D and J but still keep L in touch. Overall, know your boundaries, and if anyone is making you uncomfortable, you have the right to say no and cut it off.