I put in zoysia plugs three years ago and has filled in one side on the yard in full sun, but is struggling In an area that was in full sun three years ago but is now getting some light shade from a fast growing river birch. The struggling zoysia looks to have what I think is rust and it is also competing with the birch for water. Is it correct that high nitrogen fertilizer and warmer weather will fix the rust? I‘m also changing the mower blade soon cause the cuts look raggedy. Will zoysia choke out weeds? The struggling zoysia side has a lot of weeds I was hand pulling then spot sprayed with roundup for lawns, which didn’t seem to do anything.