some more info.... since I've been reading other older threads that might be similar.

I run the mower on the second to highest setting, leaving it fairly long. Last year I was on the highest and I was worried leaving it long last fall contributed.

I'm trying a home brew fertilizer recipe a friend uses with good results consisting of 1c epson salts, 1c hand soap, 1c ammonia, 1 bottle beer applied through a garden hose applicator. I've also applied scotts weed n feed twice this spring.

I'll get a soil sample done.

still wondering if I should power rake, maybe this summer? I don't want to do more harm than good.

Thatch can't be accurately determined unless viewed from a cross section. Cut and remove a 3" x 3" square about 4" deep so you can see the turf/soil profile from the side. Thatch will be the DEAD plant material ABOVE the identifiable soil horizon. If it is thicker than 1/2" (the existence of some thatch can be beneficial as it helps insulate the soil from heat and reduces evaporation), it can creat problems.

Weed and feed products are a bad idea. It forces you to fertilize too early, and aren't very effective at killing weeds. You also have apply them to a wet lawn, which is a no no with dry fertilizer. The fact that you used two applications this spring already is not a good sign. I wouldn't be using that homemade fertilizer either. It's probably not doing much harm, but it's probably not doing much of anything either. Also the constant application of Epsom salts will result in an overaccumulation of magnesium, which can lead to a tight soil.

OK,

What do you suggest then?

Wait for it...Lol. I'm placing $2 at the "m" window.

Well first you need to figure out why you have dead grass. From your pic it's hard to see really what you are talking about exactly. As grass1950 pointed out, thatch is a layer of dead material on the soil surface. Maybe you have thatch, but it appears as if you have areas of brown grass, probably dead unless it's dormant, but by this time of the year most grass shouldn't be dormant, even in Colorado. Grass needs only a few things; sufficient sun, sufficient water, good soil with sufficient nutrients. A soil test will help with the soil part. If you don't irrigate your grass in times of drought, it will turn brown. Is your grass getting enough water? Was your grass ever all green? Did it turn brown after the weed and feed? Do you know what type of grass you have? Are the brown areas the same type of grass as the green areas? Where are you located?