All Clubs Hit The Same Distance??

I have been away from golf for about 20 years and just picked the game back up since my fiance is an avid player.  I wasn't that great of a player before, but have seen a lot of improvement over the past couple of weeks due to the patient advice of my fiance.

The biggest mystery to me is that with all the clubs in my bag, with exception of the putter, I hit the same distance.  Doesn't matter if it's a 3-wood, 5-iron, or 8 iron.

What could be causing this and any suggestions on correcting it?

A slow swing speed can result in this,  providing your getting the ball in the air and hitting it straight with all 3 clubs.

One of the primary causes of this is casting. Don't know if this is your problem but if you cast it from the top and throw away your lag you end up decelerating and flipping your hands through impact. Instead of hitting down on the ball with a forward leaning shaft you end up doing the exact opposite which effectively increases the loft of the club and imparts way too much spin on the ball. The problem is worse with the longer clubs which explains why all your irons go the same distance.