How do I tone down the AI grass replacement on specific photos?

Use the color sliders in Basic Adjustments — select the green circle to manipulate the greens specifically, then adjust hue and saturation to get the tint you want. If you do this consistently, you can save it as a profile and apply it automatically.

Per-photo adjustment

Go to Basic Adjustments → Color → select the green circle. Adjust hue and saturation to tone down the green to your preferred level.

Automate it across all shoots

If you're doing this consistently, save it as a profile on your account. You can set it as your default exterior post-processing profile (runs on every shoot) or apply it manually in the editing gallery to selected exteriors. Saves a lot of repetitive work.