Sluggish goose, weak legs

[SunflowerFields]

Hi everyone. I have a 9 year old Chinese Goose that is not feeling well and I have never had a problem with her. I can't afford a vet bill and also none of my vets where I live treat birds. I have tried rooster booster, brewers yeast in her feed and nothing has worked. I found her Feb 20 in the back of the coop she shares with two ducks I call her babies, she gets along with them so well, I found her fluffed up in the back of the coop. Instantly I gave her rooster booster, garlic, and oregano in her water and on and off for the next week she would have good days and bad. Here we are April 9th and all she wants to do is lay down all day but she wants to eat and drink. I let her graze all she wants even laying down, she tries to clean and preen her feathers but standing is a no at least not for long. I am letting her do her thing as she wants but monitoring her eating and water drinking which I know is important. She did a nice poo (sorry tmi) yesterday that was formed but anything else seems a bit watery. Thank you for any help. I feel like a horrible goose mom but she was always my big mama and never worried about her.