Some things to check
Check the fresh water valve to the toilet. That can be overlooked when you winterize. The foot operated valve is easy to replace.
Also check the pex lines in the bath area behind the cabinets and the low water drain valves and the outdoor shower.
Since you already found one leak, I suspect something else had water in it when it got cold enough to freeze and that cracked one or more fittings somewhere. The low places where plumbing is exposed to the coldest temps are where I would start looking.
You may be able to isolate the location by pressurizing your fresh water system with air using an adapter you screw into the city water port that lets you connect to an air hose. Pressurize to about 40 PSI, Then after turning off all the taps, listen for the air escaping from the leak(s).