Rust, Stem, Stripe , or Leaf do you have it? Most newer southern varieties are rust resistant. (See UGA chart)
Now that we have that out-of-the-way, what is in your field? You could have rust. Please check to see if you have red/brown, yellow, orange or any combination of spores you can rub off onto a white cloth. (call me if you find this on a AGS variety) You need to wait two days after a rain to do this because rain will wash off the spores. Rust is very aggressive when the temperatures are right and must be controlled quickly so do not allow many days to pass before you check your fields. No spores!…….. Powdery Mildew, look for white to gray powdery fungal growth on leaves and leaf sheaths. Tip yellowing , purple leaves, and twisting of leaves BYD (it is a virus and fungicides will not control you must put out something to control aphids before you get the virus) see link below on BYD. Check out the wheat you planted against the UGA 2012 chart it will help you in determining what could be in your wheat. Lastly, you could just have cold/frost damaged wheat. We have had the right conditions to have this problem and many fields do. Yellowing, streaking, tip burn, purple tips and many other conditions are caused by frost/cold damage. I worry the real damage from the freeze will be when the heavy wheat heads lodge because the stem was weakened but not killed.
I generally find the flag leaf to be the one of the things I want to protect, the other is the wheat head. Leaf Blotch and Glume Blotch must be controlled to make good wheat yields. Fungicides do not trans-locate well and need to be on the surface they are to protect. Please wait as long as possible or if you must spray early then plan to spray twice.
Tissue test your FLAG leaf, do not get the largest in each plant as it will get the first choice of N in the plant and give you a reading on it only. I prefer to get one from the smaller tillers because that is where your yield will be increased. These smaller /later tillers will dry-up if you do not have proper fertilization.
*Information obtained from 2013 (http//www.caes.uga.edu/publications) Georgia Pest Control Handbook and Intensive Wheat Management in Georgia. As always follow label and dispose of empties properly.