Hi, my 2 months old have eczema was on s26 starter formula and advised to change to nan ha, his stool is dark green and stinks since change of formula?

It happens: Green is the color of the bile the body adds to stool during transit. It transitions through greens to yellows/browns depending on gut germ action. That & the smell has no significance. I see little evidence that such a change would alter the presence of eczema. If this was done with the idea of food allergy the protein in both formulas appears to be from the same source.