How to get my yard green? (Florida)?

it looks to me like u want organic mass put on the soil. like compost.

what i see is a bacterial or fungal blight taking over. yes u could attack it with fungicides or with biological control but those will not remain effective long term unless they are constantly renewed which gets expensive. Th real cure and prevention is to improve the turf/soil quality.

here is the long version of that explanation:

what that text will tell you is that we can isolate the particular fungi or bacteria that are invading and treat them specifically (lists all diseases and their cures) but at the same time the text will tell you that all invasions are pretty much caused by the same thing, lack of soil and grass health. And it also has a chart that
recommends specific organic materials to feed/put on your soil to improve it’s quality in certain ways. depending on which disease is taking over; like if it is a root disease which i think yours may at least partially be, then the way to feed that soil is with a sludge of organic goodness, the sludge will seep down to lower levels where root rot bacteria dwell and it will feed the soil so root rot guys will no longer be dominant.

u cannot do that if u have fertilizer on there now. u have to wait for it to wear off enough so no overdose occurs.

Reason that the fertilizer pellets are not good enough to feed the soil is because the pellets only contain 3 or maybe 7 of the nutrients that a soil and it’s inhabitants can use (typically N, P, K and maybe a few others like fe, ca or mb). So, it can keep grass green but it feeds junk food and everybody gets sick and dies. A plant will want to use around 70 different nutrients to make it’s self if it can. and who knows how much the soil inhabitants could utilize.

what i see in ur pic is that the biggest bad spot has a definable center and is almost perfectly round although it branches and joins others. perfectly round spots with a center are common in lawn disease. u can see pix here:

the low spots in a turf are where problems can start because the moisture lasts longest there and because drainage off the lawn runs there and washes away the nice soil even more. You might see a few nasty looking weeds start in the middle of that spot because they are the ones who can survive in the poor soil.

ur biggest spot does look like the lowest area. It looks like pythium root rot bacteria are there. the lawn has also the look of a few kinds of fungi on top like maybe ‘red thead’ and ‘brown patch’. What lawn disease your turf will exhibit pretty much depends on season if the grass tissue and soil structure is weak. The weak lawn tissues will host whatever disease is in season. here is disease seasons:

your local extension can tell you if cinch bugs are in season and also they have various local recommendations re grass types or water conservation, etc:

if compost goes on the soil it will help conserve water from evaporation too but mainly water savings will come from adding to the total depth of usable soil and the larger root systems of the healthier grass.

just general garden links with lawns under plants: