Inform the vendors you didn’t select.
In the sales process, you are going to win some projects and lose some projects. It’s to be expected. Not every deal is going to be a good fit. I recently had an experience that was really good. Two prospective clients actually contacted me back to let me know they were going in a different direction and didn’t pick us. I appreciate that more than they could know. It’s professional and a not so common courtesy. I wish it was different. Most prospects don’t let you know of their decision. They just go silent.