Welcome to the forum. Ashton.
While I`ve never kept Congo Tetras, I have read that they`re quite active and fast moving.
More so than most other tetras.
Generally those are behaviors that could tend to alarm discus and stress them - I do not feel they would prove to be compatible tank-mates.
I would expect you could find some more mature, near adult-sized Cardinal Tetras, Lemon Tetras or Rummy-nose Tetras, or Rasboras that would make good tank-mates, and not be eaten by discus, nor by the leopard fish.