Or do I not say anything at all?

For context: I have been sitting this dog since 2016. Over the years she has gotten gradually bigger. This time I noticed she is very overweight. I'm sure the family is busy with a 2 year old baby, but I feel like they are neglecting to take the dog on walks. Also, I am unsure what food she is fed as her kibble is kept in a large container.

So my question is, how do I bring up something like this? I'm afraid they will think I'm being rude and not want my services anymore. I want to keep them as a client not just for the money, but I love walking dogs and I really care about this dog in particular! She's sooo sweet and always wants to be pet and cuddled. I have attached some pictures here to show what she looks like.

I could really use some advice on how to handle this because I'm concerned and feel so bad for her.