#Only the Wizard would become visible; the Fighter would remain Invisible
Only the Wizard would become visible; the Fighter would remain Invisible
In context, the meaning of the phrase "the spell ends for a target" means that the spell effects no longer apply to that creature, and that if they were the last target affected by the spell, then the spell would properly end.
Spells like Invisibility often are phrased using a singular target even when they might have multiple targets. One example is with the spell Mass Suggestion, which has multiple targets yet still uses singular pronouns and grammar when describing its effects on a specific target:
Each target must make a Wisdom saving throw. On a failed save, it pursues the course of action you described to the best of its ability. The suggested course of action can continue for the entire duration. If the suggested activity can be completed in a shorter time, the spell ends when the subject finishes what it was asked to do.
[...]
If you or any of your companions damage a creature affected by this spell, the spell ends for that creature.
This sets a precedent that the phrasing of a spell "ending" is often used as colloquial shorthand for "this spell no longer affects this creature", not that the spell as a whole has literally stopped in its entirety. If the spell were intended to end for all creatures affected because one of them was no longer affected, the spell's description would say so explicitly.
