That's a nice big plant to just give it the heave-ho. I'm thinking you've had a pretty cool, rainy summer?
You could try a couple of different home-made fungicide remedies like spraying the leaves with milk, or a solution of baking soda and water. (a spoonful of soda to a liter of water) It won't 'cure' the leaves that already have spots but as the plant grows new, clean leaves if you keep the stuff on them they will stay clean.
Clean the plant up some, by removing all the dead and dying leaves right away, and throw them in the trash, don't compost them. Keep any leaves with mostly green on them, until the plant grows some new ones then keep removing the spotted ones gradually to get rid of the fungal spores.
