What is coming out of these water pipes?
So, it was something blocking the WH's outlet! Remove &amp; disassemble the Aerators for additional evidence. But, definitely flush the tank or get a Plumber &amp; sock him with that fiasco. It could be magnesium from the anode rod, an excess copper soldering flux interaction, plumbers grease (which shouldn't be anywhere), tank outlet gasket failure, tank lining deterioration or just sludge film from massive debris in the tank. But Hey, water pressure problem solved!!!