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If this problem is there either from city water or from your tank and pump system and on both sides, both hot and cold, then the most likely problem is sand or other grit in the screen filter on the end of the taps. OR it can be from debris in the intake filter at the city water hookup or filter (if you have one) on the pump. IF this is only from the cold water side, it may be some obstruction in the cold plumbing. That would be pretty rare and not affecting the hot side as well. If this is an obstruction it would have to be down towards where the pump side and city water side come together. Check any valves you have there to be sure you aren't losing pressure back into the tank. Fill valves are suspect then. Those would be the first places to check. Please get back to me if you need more on this as all follow ups are included in our fee. Plumbing diagrams would be helpful, but Forest River Customer Service pretty much sucks and those may be hard to get. If you have a good dealer it would help.
That is usually a sign of debris in the inlet screen or valve. Have you been in an area with a lot of sand? Private well system? When we run into this problem in the shop we usually take one fixture off and check it. If we find sand or calcium chunks (out of the water heater or fresh water tank) in there we can flush them out and replace the fixture. You didn't use bleach or any other chemicals in the system that may have distorted the seals perhaps? Toilets would be more likely to see that damage due to the way the valves are constructed.
If some fixtures are good, then the chances are even better it is a problem with each fixture or toilet that is having an issue.
I think you have some kind of debris in the system affecting these. Especially if you didn't change anything or have anyone working on the plumbing. Remove one of the affected fixtures and see what you find. That will give you a good idea of what the problem is with the rest.
Just checking back in to see if you were able to resolve this issue or do you still need some additional input from me here?