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.

Tube amps with output impedances greater than 1 ohm will not have a flat response into a speaker's varying impedance. They will act as tone controls! So, choose your tube amp/speakers with this consideration in mind!

Tube amps with output impedances greater than 1 ohm will not have a flat response into a speaker's varying impedance. They will act as tone controls! So, choose your tube amp/speakers with this consideration in mind!

While this is off topic, the actual situation is more complex than described above. This is because all amps make distortion, and the ear interprets distortion as tonality *unless the amp is clipping*. Apparently the brain has tipping points, where its processing of the sound changes from one portion of the brain to another- in the case of distortion, the brain can actually favor tonality caused by distortion over actual frequency response errors (or lack thereof). For this reason, an amplifier with a higher output impedance can often come off as more neutral than an amplifier with a lower output impedance, even though the latter is more 'flat'.
In the case of the OP, I think trying different taps is a good idea, and it may also be a good idea to try a different speaker cable. Tube amps have generally higher output impedances and so appear more sensitive to cables. For this reason its always a good idea to keep the speaker cables as short as possible.