Water dripping on upstair showers after shutting water main

I had to shut the water main as my hot water heater was leaking today and I had difficulty finding the water valve on the water heater. After I turned the water main valve on (I am still out of hot water as I need to replace it. I shut the water valve on the water heater) water is only dripping on the showers of the two upstairs bathroom. Water is running normally at all other faucets/toilets. Any idea what happened and what could be the remedy?

Also. I have a another question on the...

Water dripping on upstair showers after shutting water main