What has caused the black areas? Do you have standing water at times? If you use dry fertilisers you need it them to be washed in by the rain. If this doesn't happen and you add too much you could get scorching. I prefer to use liquid fertilisers because, to me, they are much more efficient. Do you wait the mandatory three days before and after cutting before adding fertilisers? The paler coloured grass is either dead or perhaps suffering from 'Red thread'. There may be some problems with English/American names but essentially it is straw coloured with a red tinge. Over here I don't believe there is a domestic treatment but I have read that high nitrogen fertilisers can help. Since your nitrogen is low there is a problem. Compaction of the soil causing poor drainage could be an issue. Do you know about forking over the lawn to improve air circulation to the roots? Another thing I have read is the use of lime on grass, especially on wet mossy ground. Lime help with improving the structure of clay soils and helps released minerals trapped inside. Another possibility is Fusarium which kills the grass and covers it in mycelium which spreads through wet conditions. I hope it isn't that because I don't think you can treat it. Have you thought about green concrete?
Sorry I can't be a bit more specific. Best Wishes.

You used to be able to treat fusarium - we did it years ago. Can't remember what we used - I guess it might have been taken off the market like so much other stuff but if you can get some it would do no harm to use it just in case its that.

Thank you for your input @cutsandgrazes and @Steragram!

I'm honestly starting to think it has something to do with the ground being really hard or compacted. I never did aerate my lawn over the fall/spring. That said however, I'm not sure as to how I should diagnose the slime that is building up.
When the grass is watered or when it rains, the lawn does drain pretty well. Though, when it does drain it seems to be spreading the green slime and causing damage throughout. I did read somewhere about grass clippings building up, which causes the mold to grow, which then creates a "hard-hat" on top of the soil. The remedy for it was to "not water the Lawn for a few days" and rake the lawn real good. The slime would then die off, but that’s hard to do when it rains here every other day. I did manage to do both but I'm back to having the slime again. Just odd, maybe the crabgrass killer I used back in March is showing its full strength...though I don’t have crabgrass anymore.

In any case I will look into both of your suggestions and go from there. I think Lime might be my next step prior to surrender, thanks for the advice. Lucky me it’s only a little backyard but it is my yard. Many thanks!

Brian

It looks like it might be a shady area, in which case you might want to switch to turf-type tall fescue. Bermudagrass can't take much shade--it needs a minimum of 6 hours of direct sun a day. It also looks a bit boggy, with those areas of black algae, which means work on the drainage, possibly with gypsum and/or compost tea, before planting the tall fescue. Aeration with a tool that removes cores will also be beneficial. Building up the nitrogen will also likely help, as long as you don't use a harsh chemical, such as urea, or ammonium sulfate or nitrate--they actually dis-improve the soil! If the site is shady, and remains wettish, roughstalk bluegrass (Poa trivialis) would work better than tall fescue.

Hi again, Your mention of slime suggests some sort of disease. You say you have scarified, which is good because most mowers, especially rotary, will leave grass which collects around the other living plants and can cause problems. Raking this 'thatch' out will allow more air to the grass roots. Poor drainage can cause moss but I didn't see any on the photos. Slime is either a disease or algae. If the latter then you must improve the drainage. When you fork holes in the lawn or take plugs out people sometimes think it unnecessary to do anything else, but you need to brush sand or something similar into then to keep them open. Other wise you have wasted your time and I've seen professionals failing to do it unless you pay more. I would not re-sow the dead areas until the problem is solved and watch out for chemical over usage. Good luck.

I would not like to have to start wrangling with your problem! I have friends in Al. (Enterprise) with a lovely lush lawn all that rain is fine, if like them, your lawn is on a steep slope with lots of drainage. The comment about green concrete, was , I hope, a joke. I can think of nothing worse! However if you cannot get grass to grow there are many beautiful gardens where the open spaces are paved with re claimed bricks or old paving slabs (new ones look far too harsh) leave gaps in the hard stuff to enable you to plant amongst them so you get a green effect right across the yard, low growing, spreading plants work well. Lawn is not an essential ingredient of a beautiful garden!
Good luck!