Sperm morthology

Ang • 34 year old female TTC for several years. Diagnosed with a traumatic brain injury 4 years ago.
Does anyone know what can possibly change in a mans sperm morthology, not the motility :) we know we have swimmers :)
In October 2013 my husband had a sperm analysis done as the first steep in our fertility issues.  At that time the analysis came back fine :). So, because he got his sperm checked At it came back fine I had to undergo more testing.  I eventually got an HSG done, and I read after its done you can possibly get pregnant right away. So the husband and I gave it some time and nothing :S so we went back to the fertility doctor in May 2015.  The hubby got his sperm checked again and this time they said it has low morthology so we need to op for <a href="https://glowing.com/glow-fertility-program">IVF</a>.  
Our thing is this. My husband doesn't do any drugs and enjoys craft beers.  So, we are wondering where the change is coming from.  Is it his diet or something we need to do to increase the morthology of the sperm?