Yes, serve an amended resopnse with a Verification.

Mr. Marman is right. Note, though, that amending your responses will not make the original answers go away. If your amended answers are more favorable to you, the other side may show both sets to the judge and/or jury and may argue that you merely changed your story for your own benefit. They may even argue that you deliberately lied the first time around.

Since you presumably signed your first responses under penalty of perjury, you should be careful about contradicting them now. And if you were (or may appear to have been) intentionally wrong the first time, you should consult with a lawyer if possible before submitting amended responses.

You not only can, you should, file amended responses a.s.a.p. A need to amend discovery responses arises routinely when there is new evidence or newly-discovered evidence; less often when errors or omissions were involved at the time of the original responses. Remember to verify your amended responses and to serve all other parties.

Definitely amend them. There is no need to file them with the court. The original verified amended responses get served by mail on opposing counsel. You might explain in your response why it is being changed -- you have now exhaustively searched your workplace for documents that refreshed your memory, had additional time to review XX or searched your own memory to determine the correct answer, were quite ill when the first responses were prepared, etc. In that way, if the new full response is read to a jury or judge, it will sound more plausible than the other party just reading the two contradictory answers. Do it as soon as possible.