Unfortunately, I'm not familiar with what you would have in your area in the way of a Local Fish Store. Being that you are down in California though, I would guess there should be some nice choices if not in Long Beach, someplace not too far away from you. That is where I would look for anoter filter sock for your system.
Back when I used filter socks, I found it was best to have 3 to 5, because I am lazy, and didn't like having to toss one in the washer every night, so I could do a change out the next night.
Speaking of the washer... when you do get some more filter socks, wash them BEFOR you use them for the first time. Just toss them into the washer, NO SOAP, and run on cold cycle. I don't know all of the technical (chemical???) reasons for this, but something in a brandy new filter sock that about kills your skimmate production, and washing it prior to usage takes care of this.
Congrats on the nitrate drop, by the way!!!
Just sit back for a couple weeks now, and watch how your tank responds. Resist the temptation of adding anything!