This happens occasionally in my RV
My bet is on the water heater. I see you live in the LA area, I live on the other end. Here's how I see this problem. The city water we get is highly treated and will keep in the tanks for a long time. Last time out, you probably filled from another water source and there is a chem reaction going on in the water heater (do a search on smell in hot water). Has to do with sulpher.
My fix has been to drain all the tanks, fresh and hot water, flush with some fresh and you should be good to go.
Norms two cents