If your representatives have already voted the way you want, is there anything to be gained in writing to them anyway?
In this situation, the representatives didn't vote. They shelved the bill, A.B. 375 [0]. Many bills don't get put up to a vote because they aren't seen as priorities or viable. This includes SOPA/PIPA which was one of the most bipartisan co-sponsored bills [1] and yet never made it to a vote because of the popular outcry such as the Internet blackout day.
[0] https://leginfo.legislature.ca.gov/faces/billHistoryClient.x...
[1] https://www.congress.gov/bill/112th-congress/house-bill/3261...