Linda,
Are the slugs bothering your hydrangeas? I have quite a few and they don't go near them at all. Maybe they are too busy looking for my hostas ;-) Anyway, we use a 10% solution on the hostas and marigolds that the slugs love with no damage. I always spray late evening or after dark with great results. Sluggo or other bait would be another option. I do both to try and keep some what control.

Sandy,

Thanks for the response! I have purchased slug bait and spread it in all areas of the gardens, because almost everything is being attacked, not just the hostas and hydrangea.
However, I don't think the dying leaves were from the ammonia after all. I really think it's a fungus of some kind because my husband insists on overhead watering of the garden. We did buy a fungicide and hope this helps.