Galvanized pipe corrodes from the inside until the walls thin out everywhere at once, and polybutylene pipe degrades with age no matter how well it was installed. Once leaks start showing up every few months in different spots, patching one section just means the next leak is somewhere else.
There is no safe first step to take alone here, since this is a whole-house issue rather than a single fixture. If a current leak is active, shut off the water at the main and note where pressure or discoloration problems have been showing up, since that history helps assess the scope.
In Bowdle, SD, the plumber we connect you with can map which runs need replacing and whether PEX or copper fits the home. Call (844) 898-0295 to get connected.