I also think that at this stage in their lives that you should be able to separate them without doing too much harm. What are you using for soil? It looks a bit heavy.
Are these seeds from a bag of NY Diesel or did you get them from a reputable seed bank?
You also need more light. See the distance that you have between the leaf sets? This is stretch and is not a good thing. It results in a thin spindly plant that has few bud sites. Tell us about your space (every indoor grow needs a dedicated grow space with adequate lighting and ventilation). Do you have a grow space set up? If so, tell us about your space--lighting, ventilation, size, RH, etc. etc. If not, we need to get you set up with something.