I saved a large agave from house remodeling. I have it in a large plastic pot, 10 gal. After a year it's looking stressed. The foliage is not the firm color as before and has lighter shades in the middle of each leaf. It gets strong light and little water. Does it need feeding or more water?
Make sure the plant is in full sun and that the soil is well draining.
You can apply a light, balanced slow release fertilizer in the spring, since your plant is confined to a pot. Use caution and do not over fertilize.
Though they generally don't need fertilizing as mature plants and over fertilizing can lead to the death of a plant.