I have an aloe that I think is a barbadensis (I found that googling pics) and the leaves seem to be losing their colour. The green is slowly fading and turning white. Is this normal? Or is it sick? I have it in a window that gets full afternoon light and have been watering it about once every two weeks. I really want to care well for this plant as it was my mother's for many, many years and I inherited it last year when she passed away. I don't really know much about plants and could use some help. Thanks!