Washer jets can leak, but you'd see rusty water around the plugs if so, remove the leads to check this. There are modified washer jets with a gasket from Ford.

It does sound like you could have a slight misfire, as when the MIL is flashing it should register a fault, even as a pending code.

edit -re-read your post and you say it doesn't flash, have not seen that before and I have worked with Focus since it was introduced!