Yes, all of your income, of any kind, is subject to tax by the state that you live in, no matter where the income is from. Since Washington has no state income tax, there is no problem of the same income being taxed by two different states.
(If you sold property in another state that also had income tax, the income would also be taxable by that state. One state or the other would give you a credit to eliminate the double taxation. But since Washington has no state income tax, this is not a consideration for you.)
I don't know whether California has different tax rates for long-term capital gains. Unlike the federal tax, most states do not have different rates for long-term capital gains. The states have one set of rates that applies to all income.
