Difficult circumstance - pictures or records of previous condition would be best. If you have receipts for the purchase of seeds that would be good. Possibly water bills showing an increase in water usage during hot dry months will help bolster your case. If your lease was up on August 16th and you informed the water company, you did the right thing. If you feel the fee is worth your troubles, you could go to small claims court and file a case If the owner is trying to sell, they are not going to want a pending small claims case against the property.
Wish you the best.
To answer your question as directly as possible; yes. It's not how good/bad of a tenant you were, it's whatever evidence they can use to back up their actions.
It will depend on the language used in the contract to begin with, and whatever evidence they may have today which works on their behalf.
I'm very sorry this is happening to you and, if you feel very strongly about this, I recommend using a lawyer to assist you in fighting over this. Otherwise, try to reason with the property manager, cut your losses and move on to better things.
You can always place a public review against them, but be sure to know that in this life sooner or later, people reap what they sow ( no pun intended ). Hope you find a good solution for your problem.
How does your inventory and condition form look?
Some property managers do what they can to keep you deposit.
They can do this and then you have to go to small claims court to try to recover.
If it really is in the same condition...then fight....if you have proof that would convince a judge or jury. Before and After pictures are excellent proof.