Check the grounds for the headlights.
PULL THE TURN SIGNAL LEVER TOWARD THE DRIVER. THAT CHANGES FROM LOW TO HIGH BEAM
use low beam lights within 300ft of on coming vehicles
The low beam lights should be set up as the outermost headlamps. All 4 will be on the when the "high beams" are switched on
The 2001 Subaru Forester has dual beam (both low and high beam are produced from the same bulb) so the low beams are in the exact same place as the high beams. Normally if your fogs are switched on and you're in low-beam mode, you should have fogs and low-beams. When you switch to high-beam, its just high-beams (fogs turn off normally). Both bulbs could be burnt out, but most likely its a fuse issue. See sources and related links below for more information on bulbs.
Sounds like it might be a bad ground
Bulbs blew
I think the low beam lamps have two filaments. So it's possible that those low beam filaments in the "low beam" lamps are burnt out. When the headlights are on dim, only the two outside bulbs burn. When the high beams are on then all four will burn.
low beams
Look at headlight lenses, if they are all clowdy, low beams will be dim and high beams will help Look at headlight lenses, if they are all clowdy, low beams will be dim and high beams will help Look at headlight lenses, if they are all clowdy, low beams will be dim and high beams will help
Dim headlights form high beam to low beam
low beam
if your low beam lights run off a relay, then that might have expired. will need replacing if it has.