Hi apples45,
In this case I think it would be easier for the EC or SM to send a letter to all residents. Especially if your garbage is becoming a problem. There is a bylaw I believe that instructs and advises how rubbish should be disposed of as in all garbage to be tied and placed in appropriate receptacle and all recycleable items the same. Could be different in your plan but I think it a good idea in the interests of maintaining a healthy happy building for the EC on behalf of the OC or the Strata manager to send a friendly letter to all residents to remind them of their obligations rather than spend too much time and money contacting individual agents as not all owners of investment properties use the same agent.
We have done so and we have now an impeccable garbage room. Some local councils also offer a service where they do a door knock in your building to advise of appropriate garbage disposal and give you a free recycle bag. We have used this in our plan. There are some times when an agent should communicate with tenants but I do not believe this is one of them. Your etc would be another thing.
Cheers CBF