You are establishing a history record for each tenant every time you send notice that you will then place as evidence at a eviction hearing.

Then NEXT TIME, if it happens, you have absolute evidence that the problem resolved and that the tenant is responsible for bringing in the roaches, or fleas, etc. 

Evidence of a downward trend line suggest that you may have to plan and execute an exit.

So I'll ask for several months bank statements with the deposit amounts evident.  

Tell a good story, support it with an over abundance of evidence, and master using the other peoples words against them...you seem to be skilled at that with the back pedaling comment.My other advice is why carpet?

No evidence of animal or human waste on the walls or floor;11. 

Keep the returned envelope UNOPENED as evidence!  

Do you plan on ripping out walls and floors to dig for evidence, thus incurring damage charges?

A landlord is entitled to ask for a description of the proposed modifications, proof that they will be done in a workman-like manner, and evidence that you are obtaining any necessary building permits.

You might not see any evidence.