You can pour the peroxide straight from the bottle until it over flows any depressions/cuped areas. If you have Physan 20, you can use it too, at the rate of 2 tsp per gallon separated by the time it takes to dry. But I wouldn't go out and buy it just for this. It will do the same thing as the peroxide. Both are surface treatments. A systemic bacteriocide, like Phyton 27, is very expensive and not easily found. Can't tell by looking at your photos if it is crown rot. The best evidence is in the leaves when they come off, if the attachment point on the now free leaf is wet looking. If it is not wet looking, we need to look else where. Bad roots, or bad bugs. But bad roots usually starts with lower leaf loss. Bad bugs could be mites, to tiny to see easily. Look at my response to this thread. I think it is the 11th entry down:
White, Dusty Splotches on leaves? .