More than likely the issue isn't the irrigation system. Being new turf or a newly installed system, most of the nutrients and loose soil remains close to the surface. This is fine until it gets hot and burns the roots. What you end up with is a vicious cycle of keeping the turf wet, but most often it is to wet.
With big systems like yours, this is next to impossible. I would consult a turf professional and have them take soil samples and recommend fertilizer schedules.
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