You might want to switch to a party consisting of Crono, Lucca, and either Marle or Frog because the next dungeon has enemies that are only hurt by specific elements. If you have either group's triple tech, you can do all elements or Just use Marle and Lucca's Anitpode to deal with Shadow elements. If you don't bring one of each element the fight might drag on, but considering you are over-leveled for this point in the game you may also be able to brute force your way through this dungeon with no problem.