I have one of those reverse osmosis systems in my house and recently the water from my sink spout and my fridge has gone down. All other water pressure is the same. I replaced the filters, still no luck. I know this is a basic plumbing issue but is there something I can do w/o calling someone?
If you replaced filters and it didn't help (was the membrane replaced too?), then the next thing I would be looking at is the R/O storage tank. Some of them use pressurized air to push the water out of the tank when an R/O faucet is open. The tank could have lost pressurization for some reason. I would check your manual to see if your system works that way, and how to check the pressure and repressurize it if needed.
Most likely there should be a valve on your tank that looks like a bike or car tire valve. Most RO tanks need around 5 pounds of pressure. ￼￼ you can check the pressure with a tire pressure gauge and pump it as required in the manual with a bike pump. But yes you should check the manual if you still have it. ￼