Softer reeds would make it worse. For sax and clarinet, harder reeds play sharper and softer reeds play flatter.

If it's a reed issue, they'd need a harder reed.

The other thing could be that the embouchure is just too loose. You don't need a lot of pressure on saxophone but you need some.

My big things on sax is that the lips are fairly loose and relaxed. There's only enough tension to maintain the shape of the natural face and prevent air from leaking out. A little pressure is applied to the reed and that comes from the jaw. It's very little.

What I'll have kids do is start with no jaw pressure and just play holding the mouthpiece with the lips. It will be flat and honky. Then I have them gradually put their teeth closer together until the sound gets better. If they continue to close their teeth then they start "biting" and sound gets tighter. It's about finding what amount of pressure sounds the best.

It's similar to centering a pitch on brass. You can buzz below pitch and above pitch but you find where the tone is best and that's when you're buzzing in the right spot.

Same thing. Too tight, too loose, just right. The sound isn't flat and honky or tight and muffled.