I already served a rent increase. Do I need to serve a another one now, after the new rent control law?

Possibly.

The new rent control law can be read in different ways. One interpretation is that any pending rent increase is void, and a new rent increase notice must be served that complies with the 90-day notice requirement, uses of mandatory form language, and is served per the new statute on serving tenant notices.

All this is far too nuanced for a quick explanation. It is best to consult with an attorney.