That isn’t b complex it’s just b12 with k. It needs to be all the b’s. The b12 is the feel good vitamin but it works along side all of the B’s to help with leg health.
I would give her the b-complex separately, not in the water, you want to get as much of that dose in that lil duckling as possible, and with ducklings half the water typically gets splashed all over the place and not consumed. Your lil one needs the full strength dose.
I would not get the second one as it's such a small amount. @casportpony can you confirm that the B-complex in @Zrach 's link above is good and confirm dosage if that is the product used?