I’m noticing that she has some grey under her collar area and a few greet hairs on her head,
She’s only 6 months is that normal?
Rottweilers do have an undercoat, it’s softer and thicker than the smooth black top coat. It can be grey or rust.
It’s often seen around the neck, behind the ears, at the base of the tail etc., usually where the coat is a little longer and thicker than elsewhere.
Having this undercoat perfectly normal and unless it’s excessive it’s nothing to worry about. Generally this undercoat is thicker, and therefore more obvious, during the winter when the whole coat is much more dense. But in the spring and summer time it can show through due to the thinning of the coat as it prepares for warmer weather.