First, stop applying fertilizer or fungicide or anything else for now. It's imperative that the PH gets up to at least a 6.0 before anything else is applied as explained in our Soil PH article. When you get a reading that's low and it's during the growing season, the use of Liquid Lime should be considered. It's fast acting and easy to apply. Most importantly, you should be able to get the PH to move up in a short amount of time. Once you get it up to over 6.0, be sure to keep watching it closely by measuring it monthly. This way you'll be able to see any movement and make adjustments as needed. Remember, anything under a 6.0 is usually bad and once the soil is down around a 5.0, it's almost impossible for the turf to utilize food properly. At this point it's hard to say if this is the only problem your soil might have but until you get it back up over 5.0, we won't be able to tell. Start applying the liquid lime right away and once you get it up over 6.0, let us know and we'll advise you on fertilizer, fungicide, etc.