DIAGNOSIS Most likely, yeah. A sudden, severe drop in flow means the filter cartridge is saturated with sediment and needs replacing, even if the light isn't red yet.
FIX Swap the filter. Unscrew the housing, remove the old PFM400C cartridge, and drop in a new one. Before you install the new one, quickly run water through the *empty* housing for a second to flush out any loose debris that settled in the bottom. Reassemble and check the flow.
IF THAT DIDN'T WORK The problem might be upstream. Unscrew the filter unit entirely and check the flow directly from your faucet's aerator (the little screen on the end). If it's also a dribble, your main faucet aerator is clogged with scale. Clean or replace that separately.
HEADS UP If you have well water or very high sediment, you might go through filters faster than the 100-gallon/3-month guideline. Consider adding a pre-filter at your main line if this happens constantly.