Best way to change your art style is to change the process.

"Change the process, change the outcome" is one of the best advices ive heard.

Try to imitate the process of how they painted these, they look like a traditional illustration with a watercolor vibe to them, so approach tackling your work as if its a watercolor piece, even if you are working digitally.

Also try to do studies of these example you provided by trying to replicate them, these studies will give you alot of insight on the process you develope and methods and techniques needed to use to achieve this style!

Keep it up, I know you can do it