Pet fee added to rent with one day's notice

Im not really sure if this is the appropriate place to ask this, and I want to preface it by acknowledging that I'm aware that TN's renters laws heavily favor the landlord.

I've been renting an apartment unit in the city for about 7 months and got an email today from the leasing office stating that they noticed I'd never been charged the one time pet fee and that they have added it and the recurring monthly pet charge to my rent. I do have a pet, and I double checked and they did in fact forget to charge me the one time fee and have not been including it on my rent since. My lease clearly indicates that I have a pet, so its not like I was lying or trying to avoid the charge, I just genuinely forgot about the charge as well.

The thing is, rent is due tomorrow and I wasn't expecting to have to drop an extra $325. Are there any requirements for a landlord to give you more than 24 hours notice before adding a fee to your rent, even in this case when it was a fee both of us forgot about? Im not trying to get out of paying it, it just feels wild that they could drop that on me with such short notice.

Am I just SOL and will have to suck it up and find the extra money by tomorrow?