Website Pages have got DeIndexed

Hello to all.

Recently since November 27 to be more specifically our website had heavy fluctuations within the SERPs. At first we thought it was just usual update fluctuations since they happen from time to time and do not affect the outcome that heavily. For the past week we have been analyzing the results and are having daily traffic drops. After further analyze we realized that the affected pages belong only to one type the landing pages we are creating for our products. The specific difference of those page compared to others is that they are dynamic pages which we fill in with content through our admin panel. Depending per product type they have similar structure and mostly we change only the content and media files within them.

Is there a possibility of this being the reason behind the drop and if so what can our next step be?
Also, if you think this might not be the primary reason would be glad if you pointed to a direction we should look at.

The only reason for this is that your content is not unique (almost identical product titles) or the internal link structure is not good enough.