Get him of the chemical poison food!!! don't wash him with shampoo ,don't brush his teeth with toothpast. Just check my other post good info
What would help to get Mangosteen very good,but you need also eat the shel"Schil". Only little bit expensive (1kg/13 euro)and hard to get. Check out the toko shops.
Dry the shell and powder it and mix it with some juice.
Make sure he get some oil, Omega 3/6/9.
Go to
www.naturalnews.com for health info very help full