I have a 7 year old G Shepherd, who has suddenly stopped eating her raw food diet. She has been on it for about 4 months. I started out making her food, then had to switch to pre-made patties. She ate that for 2-3 months and now refuses to eat it. I have tried heating up the patties slightly, adding pumpkin which she loves. She also loved the chicken wings I gave her and has become picky about those too. Any ideas?