My previous landlord is withholding commissions from my security deposit for me breaking a lease early. Is this illegal?

I gave a 30 day notice to stop my tenancy of an apartment, subsequently breaking my lease agreement. Landlord told me that if I were to find a qualified applicant to replace the vacancy that I wouldn't be charged for advertising fees, lost rent, I did. I also signed a vacating addendum which states I would be penalized 500$ for breaking lease, under the definition of 'rent-up fees'
A move-in inspection list was signed and approved by the manager for the condition i received the property in, I had a 'move-out inspection' performed by the property manager and property was returned in the condition received. Property manager stated that 500$ would be deducted from my deposit For their lost commissions. CPC 1950.5 says deposits are not for commissions and only damages or lost rent. Please HEL