Deducting it from your rent is not legal and would put you in the wrong.

I would try asking for the cleaning fee back nicely. Pointing out that the fee is illegal is not likely to get you anywhere unless you’re willing to follow that up with legal action.

This sounds like a crappy situation, the fee is too small for a reasonable person to fight it, and any action you take to withhold rent is a losing battle for you.

Ask for it back, and if they refuse, leave the place dirty enough that they won’t be able to pocket your $250