Does anyone know what these plants are? Why does one of the plant's leaves have those black spots?

The plant with light green edges and dark green center is a Corn Plant (Dracaena fragrans), possibly Corn Plant (Dracaena fragrans 'Lemon Surprise')



The plant with the solid, dark green leaves looks like Dracaena (Dracaena fragrans 'Janet Craig Compacta')



The narrow leaf plant looks like Dragon Tree (Dracaena reflexa var. angustifolia)




Or, the narrow leaf plant might be possibly Cabbage Tree (Cordyline australis)




The 3rd plant I see is a variety of Snake Plant (Dracaena trifasciata)



The black areas on the leaves are likely a watering issue. Does the container have drainage holes in the bottom?

It does. But when I got it it had been way over watered. How often should I water? When it's dry an inch down? I've watered it again since I thought it had dried out sufficiently but I maybe over watering.