While it is still too early for Brown Patch in San Fran, a related disease, Yellow Patch (aka cool season brown patch) is more common in late summer/spring, especially in cool, wet weather. Most of the conditions for yellow patch are similar: wet turf, over application of nitrogen fertilizers, reduced air movement, etc. Mowing tall fescue to 3.75 inches means that it will probably be 5 or more inches when cut. This will greatly increase the chance of developing yellow patch, especially in a typically cool and wet environment like San Fran in the spring. The link I attached showed that mowing tall fescue lower is a valid cultural practice that will product better turf, that is less likely to be affected by certain diseases. In fact it makes more sense to mow lower in a climate like San Fran anyway where there is less summer stress. To the OP, it's your lawn, you can mow at any height you want, but I personally do not subscribe to the advice of "Mow as high as possible, or on the highest setting." First of all it lacks an actual unit of length. Second, what if my mower goes to 5 inches, should I mow it then? Third, I mow in the range that is recommended by the seed producer, as well as most universities.

"When all you have is a hammer, everything looks like a nail." I think that came out wrong. I was not hinting at anything you said. I was setting up for what I was about to say. My hammer is corn meal, which in the organic world is recognized as a fungal disease preventer and cure. The nail is your yellow grass. When I see the yellow grass, I assume it is a fungal problem. I can see where that could easily be misinterpreted. Sorry. YES, you have to wait until late summer to reseed. Why? Well you don't have to but if you want good results, wait. Seeding now will give you a yard full of crabgrass right away and later on, any grass that did germinate will die from the heat allowing the crabgrass to fully take over. If you want to fix that for the future, you could seed in some Kentucky bluegrass in the late summer. It will spread to fill in weak spots where fescues do not spread.

Symptoms sound a lot like a fungus which is what crown rot is . This link has pictures that might help you nail the problem especially : FIGURE 3. Patterns of leaf discoloration produced by Liriope leaf and crown rot. This is the recommendation of a fix : Avoid plant crowding, planting too deep, and over-watering. Do not plant Liriope where there is a likelihood of frequent flooding or collection of excessive surface runoff. Where leaf and crown rot is already present, planting Liriope cultivars that are not highly susceptible to the disease is one possible solution. Presently-available fungicides probably have limited use in the landscape because they are costly and temporarily suppress, but do not cure, leaf and crown rot . Avoid soils with high organic and peat moss content . Here is a link that might be useful: Leaf and Crown Rot of Liriope

Texasturbo I live in Austin 1st rule of thumb is never plant mondo aka monkey grass in the sun it will fry even in a mild summer even in Dallas.The liriope or lily turf is a good suggestion in fact lots of people (as you can see confuse the two). WoolyStemodia(ok in Austin not the metroplex) and Bulbine would not be reliably cold hardy in the metroplex .Low growing sedums are a good idea if you want some there year after year.Perennial color Homestead purple verbena or Blue princess Verbena (Found growing in England by Greg Grant)yes it takes the heat too.There are some annual Salvias like S. coccinea "Forrest Fire" or "Coral Nymph" others like purslane do well in the heat then Pansies or dianthus for winter. Pansies will need watering though if winter is dry. it is a dry winter.You have some good gardening information from Howard Garrett (Plants of the metroplex)or Neal Sperry who has a gardening show on KRLD 1080am Saturday & Sunday from 8-11am. Have fun!!