Should my All Porcelain Crowns Have These Gaps Between the Crown and Gum Line at the Back?

From the appearance of your picture, it looks like there could either be a gap between your crown and your tooth, or there is a ledge formed at the junction where the crown ends and the tooth starts.  A gap may be able to be sealed to prolong the life of the crown and prevent food from getting caught, a ledge should be able to be recontoured so the crown and tooth are flush with eachother.  If the gap is too big, you may have to have the crowns redone.  These types of issues with crowns (and any kind of tooth restoration for that matter) should be dealt with since they are areas that are more susceptible to the development of decay (cavities).

The picture is very blurry and cannot be used to diagnose. There should NOT be a gap between the porcelain and your tooth. The porcelain does not necessarily have to go all the way to the gumline, but it should be flush with your tooth enamel wherever they meet. There should be no space between the 2, and there should be no ledge either.