Neither of the first two nor anything else ending in a question mark unless you're really asking a question.

Not #3 because you're still being coy.

I'd suggest #4 or #5 when dealing with peers but they aren't interchangeable, they mean different things.

Save #6 for when you're giving tons of feedback to a junior.

If you're worried about being perceived as harsh or unfriendly, remember you can still be super friendly in the chatter on either side of the review session.