>>2931230 (OP)Contractor here. See the colors? Someone used pvc (white) fittings on cpvc (yellow) pipe.
That's gonna require complete replacement. In an occupied house it can suck to do this work. If possible run all the new pipes in addition to the existing and then swap the feeds and connections all the same day. If not, you'll need to figure out a different strategy.
I use Uponor pex, white only. Buying blue and red will waste more material. Nylon fittings. If you don't want to use expansion pex stainless cinch rings are next best.
Build manifolds at the beginning, with shutoffs on each feed. Run 3/4" lines to each room. T off those into1/2" to individual fixtures.
Pipe will run $500-600. Fitting will be $200 more at most. The rest is labor and maybe sheetrock repair. You can do it.