If the bounce rate is high, that usually means that (i) the website is unappealing or it isn't obvious where to go or what to do, or (ii) the website is punching above its weight in the search engines and getting traffic that doesn't belong there at all.
New sites sometimes do get a 'honeymoon period' where Google puts them high up the rankings because they are new and fresh and exciting, but they then fall back down to their "real" level in time. That may be what has happened here, if you haven't made any other changes, but wouldn't explain why the bounce rate has increased so much all of a sudden.
If you want a more detailed answer as to where your site might be going wrong, you're welcome to post a review request (please note that before you are eligible to ask for a review there you need have reviewed at least 3 other websites with a substantial (i.e. more than just "nice", "I like it", etc) reviews.), where people will be able to look at the site and give you feedback on whether they would bounce and why.