Do they breed at both facilities?
I do find it interesting Masai Giraffe are well-established in Ohio and California zoos but most of the the Wisconsin/Illinois/Missouri corridor as well as Minnesota and Indiana is focused on generic with a couple of small exceptions. Racine just has the one individual, Potawatomi has a few, and Kansas City Zoo has a herd but they are off display while their habitat is under renovation. Brookfield, Lincoln Park, Milwaukee, NEW Zoo, Indianapolis, Mesker Park. Fort Wayne, Saint Louis, and Como focus on generic, and Henry Vilas looks poised to return... this all looks quirky though when one considers all four of Ohio's major zoos (Cleveland, Cincinnati, Columbus and Toledo) seem to hold Masai or both.
This thread has more information. I'm no expert but the gist of it is that there isn't as much genetic diversity in the Masai population so not as many births are successful / survive.