Yes, it is something to worry about. You need to separate that baby from them ASAP. First, you should never put new leos together, they need to be quarantined for at least 60 days, unless you want to chance all your leos getting sick. I don't know if there is a big size difference between them or not, but it really doesn't matter at this point, at least one has shown aggressiveness towards the new one. Chances are the baby is not going to get to eat and will stay hidden most of the time. Not to mention if one of the others attack it, it may drop it's tail or end up with other injuries. As far as housing multiple leos, you should only house females of about the same size together, but not all females will tolerate others. And never attempt to house 2 males together they will fight and one could end up dead.
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