A. I don’t think the artificial grass has anything to do with it. I suspect that maybe the soil is being kept too moist. The artificial turfgrass may be acting like mulch and keeping the soil wet longer than if it were not covered in anything.
Water deep and infrequently. It should do okay watered twice a week now with about 20 gallons or so each time.
Try getting some iron chelate spray and spray the foliage in the cool morning hours. Add some spreader to the spray to get it to go into the leaves or use some liquid detergent but be careful of store bought liquid detergents. It is possible they can cause some leaf damage if you aren’t careful with them.
You have to spray liquid iron about four times; once every couple of days for four sprays total. Spray until the iron solution drips from the leaves. Make a new batch each time you spray and use the spray fresh each time because of our alkaline water.