I don't know if there are specific exercises to fix it, but I know you need to avoid all ab work that requires a curling up motion, like sit ups, toes to bar, knees to elbows and hollow rocks. Core work you can do are planks and push ups, overhead squats, press and push press. These require mid line stabilization but won't make the separation worse.
thank you Andrea! I guess I will just do some really easy ab workout that require only "squeezing" the belly in.. hopefully it will go back to normal soon