There are a couple of nutrient deficiencies that can cause leaves to be yellow/ exhibit chlorosis. One is iron which becomes more limited as pH increases, so adding a lime source would make the problem worse.

Given the time it would take those shells to even begin to be digested and add their calcium to the soil (years), provided there was even an active Soil Food Web in that container soil, it is not worth the time and effort.

Perhaps this article on plant chlorosis may be of more help.

http://extension.illinois.edu/focus/index.cfm?problem=chlorosis

Okay thanks, I didn't realize it'd be that slow. I just know where the bags spilled last year a weed that prefers alkaline soils is the only thing growing there now so I thought it'd be quicker. I added a little anyways to the neutral new soil. Hopefully it'll be enough for a garden hybrid one.