That should have killed the mould but the stains won't go away they may fade in time ........... You can mix up a strong brew of tea in a bucket, strain the leaves out then spray the brew onto the canvas, inside and out, a good soaking and it will give a khaki type colour, may need a couple of goes, you can use coffee instead, even heard of using a water based wood stain ..............
Once its all dry then grab a big bottle of oilskin coat waterproofing liquid, not the spray can rubbish, spray it over the canvas, if you give it a good soak with that yearly it will keep the moisture out, just never fold away when damp, well open up to dry soonest if you do ... I also rub some wax stick over the stitching to keep it sealed....... If the canvas starts to fall apart before it goes too far find a Canvas Shop a place that makes tarps and things, they can make you a new bed end far better and cheaper than a dealer and you can get better screen material as well, just remove it and it will be heaps cheaper.