*Tmi for sad photos*

Has anyone else had this happen to their dog? I noticed that she was all of a sudden starting to become really skinny, so I asked you guys what to do and you said I wasn't feeding her enough and to up her food intake. I did so and it's only been 1 week and I've seen massive change! She is almost as filled out and healthy looking as before. Is this normal?

*added* She is wormed and fully vaccinated.

Before weight loss:

Sudden weight loss:

Now: