St. Augustine is yellow
Im not a professional, but a homeowner who likes to do lawn work. I live in the DFW area of Texas.
My front yard is bermuda and I have had bermuda forever and have learned how to take care of it pretty well. Right now my front yard almost looks like a magazine with dark green, thick carpet look.
However, my backyard has a mix of bermuda and st. augustine. a year or two ago I put down some st. augustine sod in some shaded areas and its kinda taking over (which i dont mind). So in my backyard, I havent put down ANY weed killer at all and have only put down a scotts fertilizer and ironite this year. The bermuda in the backyard looks great, but where the st. augustine is, is yellow.
However, all the new runners and some areas of the st. augustine looks great and dark green. I dug up a little patch and took it to a local garden and my Lowes and they both said it didnt look like I had a disease or bugs, but looked like possibly over watering.
So i cut back and have only been watering the yard once a week for about 15 mins each zone in the backyard. Well apparently that is not enough because its getting really dried out and wilting, so i water a little more. its been about 1-2 months now of trying less water, more water, ironite, greensand, etc and nothing is making it dark healthy looking green.