I feed my kids eggs. NOT my plants. Egg shells have beneficial coponents that will release as the shell decays in the soil.
As far as an egg goes...save it for the frying pan. You need to get some nutrients. Preferably ORGANIC.
That egg you put in there can and will cause unwanted life like mold or fungus. I would do my best to flush that out of the soil. Then get you some Fox Farms Organic or equivalent. Don't take yellow leaves off untill your sure they are dead.
You'll know they are dead when they come off the plant with very little effort.