Voice of Ra: does "all skill checks" apply to all players or just the caster?

Question

Voice of Ra states

You may cast and exhaust to gain +1 to all skill checks for the rest of this turn.

Is that all skill checks for the caster, or for all investigators?

Answer 1

It's just the caster, i.e. the "you" at the beginning of the sentence. Same way casting Wither or wielding a weapon only helps your combat checks.

Answer 2

You may cast and exhaust to gain +1 to all skill checks for the rest of this turn.