My coaches horse that i ride is allergic to corn. She bought the same feed all the time but the company made a mistake, and put different feed into he same looking bag. I got dumped on my ass so many times that summer. luckily my coach noticed the feed inside the bag looked a liitle different so she called the company ASAP
I have not made any changes to her feed. We did just recently move her to a new stable. I know it is a little colder than usual. No one else has been riding her and other that we have changed nothing. Thx for the suggestions!
This change can come with a change in feed, surroundings, temperature/weather (this would make a lot of sense if it is winter where you are. Horses are usually really fresh when it's cold), change in horses around them, or moving to a new location. It can also come if their amount of turnout has suddenly changed. Are there other people who have been riding her? If they are unconfident in themselves, they may have transferred some of that fright to her.