I agree it looks like rust disease on your grass.  If you have too much to hand snip out the infected blades then fertilize and try to keep the grass very dry. This is a fungal infection that needs moisture. I do not think you need to be too worried as summer is coming and the dry weather should help your grass to overcome the problem. If it gets worse, you can consider the more drastic action of cutting the grass to within on inch of the ground. Fresh new growth should pop up. Keep growing, Marianne Binetti