I don't think I understand your post... you think you poisoned your dog by feeding Blue Buffalo food? You mention a Senior Lamb and RIce formula... Blue Buffalo only makes a chicken formula for their Senior food. They DO make a lamb and rice adult food, and the lamb that they use is human grade meat, very high quality. Lamb is their only imported ingredient, but it is imported from New Zealand, a nation that takes quality control for their lamb exports VERY seriously, and the New Zealand lamb is then processed through a USDA facility. Very good quality, and very good quality control.

I too do not understand the original post.
First of all, yes your dog will be gassey and have soft stool- initially- if you do not properly change over a new food to a prevously fed food. Come on! Common knowledge! This food is also one of the most potent foods and healthiest foods you can feed to a k9 or carnivor. Its as raw as you can get next to feeding a slab of steak or meat. As far as poisoning? I am so sorry that you lost a friend, but I dont think you poisoned your friend. Shocked its system with high doses of protein? probable. You try eating one type of food and then stopping to start anoter new. Thats wicked high in protein. I guarantee you will be visiting the toilet more too. And diahrrea dehydrates you thus = weight loss.
Colorful packaging? I truthfully think you are thinking Solid Gold brand- theirs is glittery and colorful. And kinda similar. Blue isnt a product thats sells by its packaging. It sells cause its an awesome food that has so much thought put into the nutritional safety of our animal friends.
Its always so much easier to blame someone or someting else for your mistake.