What are a tenant's rights against landlord who is demanding additional fees that were not part of the original lease agreement

Landlord and tenant relation: I live in an apartment in Colorado Springs, Colorado. I was one day past the grace period when I turned in rent this month, and now my apartment complex is trying to make me pay not only a 50 dollar late fee, but also the 363 dollars for the concession rate of our apartment. And i have to pay this 413 dollars by the 10th. It is in our lease but is this completely legal or is there any way to get out of it? - Is this your question? Add additional information