I think my harbor Bermuda is reverting back to common

last 2 years my yields have been going down In yield we have been getting plenty of rain and my soil test are always great with PH around 6.9 i fertilize after every cutting with 450lb of 22-11-22 I spray prowell h20 in spring and 24d in may if I have any weeds so trying to figure out what I did wrong or what went or is going wrong as I have really been trying to take care of this field. The field has always been In row crop and took it out and had it sprigged 5 years ago with midland 99 and the first 3 years yields were amazing with a 80 small square a acer average. Last year I had about a 45 bale average so been trying to figure out what is going on but could never really figure anything out. I walked the field today and the outside looks amazing knee high hybrid Bermuda just as pretty and thick as it could be but when you walk out towards the middle it is Poor and thin with what looks like common Bermuda there are places that are not ankle high my pastures look better. I noticed this about 3 weeks ago after my first fertilizer application of 450lb a acer of 22-11-22 seamed not to do much so last week I spread a little more urea on it just to see what it would do and it just doesn’t want to grow so i really not sure what to do at this point.

I think my harbor Bermuda is reverting back to common