Tenants Left before end or tenancy

Tenancy Deposits

Hi, my tenants left just after 4 month. They gave me one month notice. But tenancy agreement is for 6 month. I have deducted 15 days rent as it was mentioned in agreement that if they leave the property before end of tenancy I can charge them until property is not rented again.

Also they broke kitchen cabinet which I charge them and they left property very dirty which I charge them.

Now they are disputing that I should return deposit. First they said they don’t know this was written in contract. Now they are saying I have ask them verbally to leave the property which I never.
Now they want to take this matter to court. Where I stand as landlord.

Any advice will be appricated.
Thanks
Ba