It looks to me like either grass rust or Anthracnose. If it is like a redish powder covering the grass that will come off on your hands when you rub it then it is rust and if the blades have turned red than most likely it is anthracnose. Here is a link to a lawn disease page. http://www.bayeradvanced.com/guides/disease?gclid=CL6a_4ny67ACFUlN4AodZjd7tQ
We have some other members who may be more experienced with this area than I am but the conditions you describe make it sound more like Anthrcnose which happens when there is lots of rain. Rust happens more when it is dry.
There are lots of things you can do on your own to improve your lawn. First off I would suggest getting a soil test to find out what your soil is lacking. It is not terribly expensive and it will help you find your problems. You don't say where you are which can sometimes help us but if you do an internet search for "soil test" and the name of your state you should find a lot of options for a good soil test. The do it yourself soil tests sold at some nursery and garden centers are pretty much worthless. Many state universitys will do a soil test for you and there are a number of commercial labs specializing in soil tests. When you do the test take soil from several different locations in your yard and mix them together. This gives a more accurate profile of your soil.
Just looking at the photos it looks to me like it is lacking in nitrogen. I am wondering what kind of fertilzer you used when you fertilized? I am asking if you remember the numbers on the bag, like 25-10-5 for example? You do want to be careful fertilzing this time of year. Too much nitrogen in the hot weather can burn out your lawn. If you do more fertilizing it might help but go a lighter application than the bag recommends and water it frequently.
You should have little difficulty setting up a program of your own that will give you a nice lawn without a lot of expense. A schedule of applying weed and feed, crabgrass preventer if you get crabgrass and fertilzer alone should go a long way. Over the long haul occasionally core aerating (you can rent a machine from a rental center and perhaps topdressing with compost are other things that can help to give you a great lawn.