朗晞媽媽, I am also "Long Hei" Mama, but my Long Hei has different chinese character...he is now 1.5 yrs old la...
My Hei had exactly the same problem as yours when he was about 2 weeks old and eating A+
Then I took him to see two doctors and both of them suggested him to have Snow Brand Smart Baby, then both poo poo and skin turned to very good quality within 3 days! Till now, he is still taking Snow Brand and having white and smooth skin, it is suitable for him as he is "hot base"!