upvc roof

[spoonse]

I have a lean to-with upvc paneling roof which has hollow inside and airflow cubed type gaps all the way through/if you can understand as its hard to describe .The end cap of one of the panels has come loose which is the end that runs into the gutter pipe and a silty green stain is now forming on the inside of the airflow strips.Just wanted to ask if anyone knows of anything i can use to clean it out with ,bearing in mind there is only about a 10-15mm gap on each hole?

Thanks