The owner may recover from the tenant any excessive amount deducted from the rent. The amount deducted shall be excessive to the extent that it exceeded four months' rent as calculated pursuant to the preceding paragraph, or if it was unreasonable under all the circumstances. The criteria for unreasonableness shall include, but are not limited to, the alternatives available to the tenant at the time the violations were first reported, the urgency of the need to repair, and the quality and cost of the work done. Any excess deducted may be recovered in an action in contract, but not in an action for possession of the rental premises. The terms of such recovery may include an increase in rent for such future periods as the court may order. No owner may increase rents because of repairs made pursuant to this section, except pursuant to such a court order, and the provisions of section eighteen of chapter one hundred eighty-six shall apply to any such increase in rent.