Hi and welcome to the forum! Most of the time when snakes refuse to eat it's bc one of two (actually three) reasons. The animal is living under less than optimal conditions due to husbandry issues. The animal is ill or the animal is breeding. So, husbandry , I think would include acclimating to a new enviornment also. You mentioned that it's been four days? Does that mean you have had them for 4 days as in recently purchased or 4 days since they have eaten ? Ok, I see where you mentioned they haven't eaten in a week. What size enclosure are they in? Are they all living together? If so, they may be stressed right now. How were they being housed by the person you purchased them from might shed some light on why they are not interested in the fish. For now I would focus on my husbandry and set up and begin tweaking that to start. Good luck. Keep us posted. Remember also young snakes love to hide as do mostly all snakes so maybe add a extra hide or hides. When they are used to certain foods it may be a while b4 they accept something different too.