Unless you've posted the second and third pictures before, you are NOT the artist, because I've seen them somewhere else.
The first one you obviously didn't do, as it states it's a line drawing by someone else.
I think the first one is an example of a collaboration.. You know.. One person does the lines and the other one colours it. (Hence the credit of the lines to the artist and the credit of the colouring from Pony10girl) A lot of people do it on deviantART. And the second picture is from one of her other threads in the "Horse Artwork" section.