Maya wouldn’t be Maya without multiple ways to do things. Here are two ways of controlling the speeds of multiple MASH networks in the same scene.
Option 1: Multiple Time nodes with an expression
-Make a second Maya time node and connect it to the same MASH nodes.
-Connect it to the same MASH nodes
-Write an expression like in the screenshot that connects it to the original time node but modifies it.
Option 2: Math nodes between Maya Time and the given MASH network time.
Instead of making a second time node you can connect a multiplyDivide node between Maya time and other MASH networks to modify the values getting fed into their time.