Tiiu is naturally "skinny", cuz her upper part is very skinny, but her legs look healthy to me!
I'm not so sure about Hana, she's always been skinny, since she started modelling and that was very early, as far as i know. But Snejana is too skinny, ok maybe she is naturally skinny, but not so much. Cuz if she would be naturally so skinny, she wouldn't look so tired and without energy, i don't believe anyone who says that it's just the way she is.
Karolina used to be very skinny, but then all of sudden she got more curves ... hm, did she start eating? (I think she looks much better now )