Hi
That looks completely normal stool especially after starting a new supplementary feed
Next Steps
Please observe for the danger signs like Baby becoming dull..not passing urin atleast once in 6 hrs while awake or once in 12 hrs while asleep or lips and tongue becoming dry..Make sire to give adequate fluids so that he won't be dehydrated..Any of these signs as mentioned conilt your pediatrician as it indicates dehydration.
Health Tips
WATER AT FREQUENT SIPS TO AVOID DEHYDRATION