Looks like frass, and there are chewed leaves. Probably there are caterpillar or beetle, or other pest hiding in the plant, some pest are nocturnal and at daytime will hide at the base of the plant, under the pot, or dug into the soil.
The chewed foliage reminded me of grasshopper damage but the frass/excrement definitely looks like that of a caterpillar, or possibly a slug. If you aren't seeing any pests on the porch in the daytime, it's most likely a caterpillar, or slug feeding at night. After dark, take a flashlight out onto the porch and shine it around your plant(s); closely check the potting soil and also lift a few leaves to check the undersides. I bet you will find the pest!
~ I'm an old gal who still loves playing in the dirt!
~ Playing in the dirt is my therapy ... and I'm in therapy a lot!
