I wouldn't federalize any of your bonsai, you might end up owing taxes on them or having to give them up to the government
Only joking, yes you can probably start with some fertilizer right now. Something like an Osmocote slow release would work to give you steady feeding over the next 5-6 months.
If you are using irrigation water in Southern California, consider an acid fertilizer like Miracid or Super Iron 9-9-9. And make sure you protect your tree from the Santa Anas.