My new lawn planted in the fall may have been overwatered--looks yellow and full of weeds and broad leafed grasses (crab). Actual grass looks very weak with short stunted growth. Any way to fix the problem?
Overwatering is much less likely to be the problem than some other things like problems with soil composition, type of grass, fertilization, insect and weed control, or disease. Growing a successful lawn is not easy - that's why many people turn the project over to professionals. If you want to do it yourself, it will require quite a bit of study, a lot of work, and major patience because success doesn't happen overnight. Here are some articles that should help you first figure out what the problem is, then what to do about it: https://www.gardeningknowhow.com/lawn-care/lgen/so-you-want-your-grass-to-grow.htm