Why did Tameka Raymond lose custody of her two children?

First she lost a son and now Usher has full custody of the little ones. How Tameka lost custody of her children is amazing to me. I thought the courts were more sympathetic to mothers? This must be hard for her; losing one son in death and two more in a custody battle.

Anyway, after losing custody of her two sons to Usher, Tameka Tweeted this...

Kinda feel bad for her

Why did Tameka Raymond lose custody of her two children?