Purchased a replacement filter - Samsung - from a big box home appliance store and installed it according to directions. Let water flow for several gallons - again, according to the directions on the package.
Worked well for a week, and then water flow began dropping. Now it takes more than 20 seconds to fill a 6 oz juice glass.
Everything else - faucet position, water pressure, plumbing setup remains unchanged.
Possible a defective filter? I dont know.