Thamnophis.UK
Dedicated to the captive husbandry of Garter Snakes.

I was speaking to a friend who has noticed some of his baby Garter Snakes developing spinal kinks as they grow.  I suggested to him that his choice of diet by be at fault, although he thinks this is not the case.  Any thoughts?

Depends on the diet, suppose. It is plausible.

It can also be a problem that started during the embryonal phase for some reason and which gets worse during the growth.

When it is only present in animals of the same litter, than the above is a good explaination. If it also is present in animals of other litters/species, than I would also think it is a care/food/vitamin/mineral problem. And when the problem does not occur in animals of the same litter(-s) which are sold to other people, than it  has to be a care/food/vitamin/mineral problem.

A solution for the problem I have not.