Problem related to Push-Pull or EL34?

 Push-Pull design in itself does not increase the bass and make the sound a little boomy.

EL34 tubes by design do not emphasize bass frequencies.

The choice of capacitors is significant in the sonics and performance of an amp. But so is the design and implementation.
Very simply put, Push-pull design has more power and less distortion than a single-ended amp. A PP amp can also operate in either Class A or A/B, so this affects the sound produced.

In your case, it could be the tubes installed. Input tubes, especially gain, and the output tubes can emphasize bass or any other area of the frequency spectrum. Your EL34 amp may need output tubes which are more linear. 
   Another consideration is power. Is this amp powerful enough to drive the speakers. You need enough current to push the bass drivers.
And then there's the room. Bass frequencies may need absorbion, there may be standing waves creating more bass in your music.

 

In my limited experience, all things being equal, e.g., power rating, cables, speakers, etc., the tube amps with higher output impedance/low damping factor tend to have a more boomy bass response. You can try a different output tap, 4 ohm vs. 8 ohm, and see if that makes a positive difference.

Good idea on trying a different output impedance. Also true about damping factor.
I expect some expects will weigh in about this.