I'll assume this moisture related
Well, you beak the stressed parts out to their own zone, the. Increase the co for this/these zones.
Or Increase the co for the existing zones but you run a small risk of overwatering parts of these zones.
Or Cut down the oaks.
You are loosing water outside of the model's functions....
If it is light related, get a rye or some hybrid that has lower light requirements.