When we turn the hot or cold water on the pressure seems fine but within seconds the water becomes just above a trickle. This only happens in the master bath and not in the kids bathroom. We did have a knocking before the pressure would drop but now the pressure just drops.

What type of faucet do you have? You can shut off the valves under the sink, and try disconnecting the supply lines from the faucet and run some water in a bucket to make sure that you have good pressure from the supply lines. If you have good pressure then the problem is in the faucet. Take the aierator off the spout and check for debre, rinse and reinstall on faucet. Try it and see what happens. Let us know what you find. Goodluck ---zeke---