Overfertilizing turfgrass thins the cell walls of the plants leaving them weak and less tolerant to disease and insect damage.
BUT, if a lawn is weak and thin, I can get good results by applying a fert like 20-10-10. I would use it at 8 lbs/1000 square feet (that is about 1 -50 lb bag). But I would only do this ONCE and during a time when rainfall is adequate. I've pulled many ugly lawns out of a slump.