Nothing is good enough, ready to walk!

[diamond457]

Im a supervisor at work and I work alongside my manager and the other supervisor. The manager and the other supervisor are a couple and I feel like its always two against one. My job is to do their roles when they are not in work. They are off on the same days so I am left sole charge.
I work with animals and my job is to look after the animals and supervise the staff. I do my job to the best of my ability and I am qualified for the job with a good amount of experience.
The trouble is that no matter how much work or effort I put in its never good enough. The staff havent had any complaints so far either so its not like the staff have a problem with me.
When they go into work the next day they complain about something small thats not to their liking or not done the way they usually do it. I always get a text to say there was a problem or another. Its really starting to get me down as its always something so silly that doesnt even matter. One time the supervisor knocked over a bucket of something and left it on the floor with a note left for me the next day saying he spilled it because someone had made it too watery. What I got from that note was that because it was watery he made a mess and he shouldn't clean it up because its my fault that he spilled it! I was pretty shocked at that.
Its just nit picking constantly and I feel I can't win no matter what I do.
My boss can just be just as bad as the other supervisor and I think it makes it worse because they are a couple, they are on eachothers side and have been there longer than me.
I don't know what to do anymore. Put up with it? Rant it out? leave?