[Landlord - US - WI] - Late Fee Evaluation

Long term tenants of 4 years in small single family home @ $1225/month.

I’ve been too lenient. History of late rent and my patience ran out earlier in the year and stated no forgiveness on late fees going forward. I was not enforcing them.

Lo and behold the primary breadwinner lost their job shortly thereafter, now 2 full months behind and going on to 3.

I have $10/day late fees on the agreement passed grace period.

I want to make sure I have the late fee statutes correct for late fee evaluation.

I understand it shouldn’t ever get to this point but a snapshot in time of the situation:

November would be 54 days late= $540 late fee.

December, no grace period because November wasn’t paid. 29 days late = $290 late fee.

Question #1: Is compounding daily fees allowable with multiple months outstanding?

I am not trying to burry these people in fees but I want my facts correct and lawful for move out negotiations. Month to month currently, so notice will have to come formally shortly.

Confirmation #1 Statutes on fees seem to be open to interpretation as long as they are reasonable and I understand there is no cap?

Not excited about sending a young family out the door but I think that is the reality I face.

Thank you for any insight. Would prefer to avoid court.