Pink chin and other issues

[VMoz]

Hi all, I've just joined. Chewie, my 9 month old, is my first GSD. I'm surprised every month at how high maintenance this breed is compared to other dogs I've had over the years. It seems like I'm always fretting about something. At the moment we have a few issues at hand. Im hoping you all can weigh in with thoughts and or suggestions...

1) for the second time, she's developed a pink hairless patch on her chin. The first one went away but this one is sticking around 2 weeks now and no change. It doesn't seem to bother her at all but I'm wondering what it is.

2) our vet told me that she thinks Chewie's back leg muscles are a tad underdeveloped for her age. I keep hearing that I'm not supposed to take her on long walks or runs until at least one year old to protect her hips from any damage. She still won't jump into the back of our SUV on her own so I'm wondering if she does have weak back legs. Is there anything that I can or should be doing about this?

3) just recently she has decided to stop eating breakfast. We feed her blue buffalo large breed puppy and she used to love it. Now she won't touch it. Around 6pm she finally gives in and eats a bowl but she still isn't eating the full recommended amount that she used to eat due to skipping her breakfast. Is this common?