I have a very close friend who lives outside of Baltimore, MD. He is an avid DIY'er. He has a mature zoysia lawn,waters regularly, de-thatches at least annually. No airation. He uses Scott's products. No pre-em this year but did weed-feed mid April, probably before the grass was not out of dormancy completely. He tells me he did a heavy de-thatch last fall. The lawn was coming in well this spring. However, a few of the late starting areas, some latent browning, died off leaving bald areas. I suggested, again, changing his fert program to a specialist, waiting a little longer to feed, re-plugging in heavy de-thatched areas. Any other suggestions please??!!