Will you be able to visit all three? I think they are all peers academically but pretty different environments. If you don’t have a clear favorite, I would not ED.
We visited both Bucknell and Lehigh and felt the vibe was very different between the two. Bucknell is much smaller, more rural, has more greek participation and my daughter thought it had more of a “country club vibe” (which in her mind meant students seemed to be more affluent). Bucknell felt to us more like an LAC.
Lehigh is in the small city of Bethlehem, gorgeous hilly campus, student population felt more diverse to my D, and a bit more of a pre-professional. Campus and the surrounding area also felt “livelier” to our D.
I can’t speak to Tulane but I expect that being in NOLA would make for a markedly different experience.