There are a few possibilities, but it's hard to know without closeups and descriptions of how the disease progressed, if it is in fact disease. Being in Colorado I am assuming it hasn't been hot and humid lately. What has the weather been like? Have you had a lot of rain before you noticed these areas?

i'm with tiemco, really hard to tell without closeups of the grass blades. it may not be disease, could be something else.

How have you been watering since April? How often and for how long?

Hi

Thanks for your comments. The watering schedule we have is 20 minutes per zone, twice a week, starting at 5am. It hasn't been hot or humid, a few days in the upper 80s but not really hot with cool nights.

Other than those problem spots, grass is doing wonderfully. I only noticed those areas when the rest of the grass turned nice and green, and those areas remained brown. I have included six close-up pictures.

There are some wild rabbits in the area, do they cause urine damage like pets?

Regards,

RamonOsuna

Here is a link that might be useful: 6 more pictures