Question
my lawn has irregular light brown spots (sizeable) that has no pattern.  recently fertilized which greened up whole lawn except these many spots.  Color of spots are light brown/burned looking.  no regular shape, lawn gets full sun, some spots the size of apples and larger ones the size of 3 to 4 feet irregular pattern. We live in lakewood wa, and spots were there before we fertilized it.  Spots seem to be growing/increasing.

Answer
It does not sound like lawn disease, but it could be. Check for grubs first. If you can pull out the dead grass like lifting a carpet it is probably grubs. You can also dig into an area which is half dead/half green and investigate the root zone. if you find white c-shaped white maggits, you need to put a grubicide down (e.g. Grub-Ex). Apply now and repeat June.

If it is lawn disease, you can put down an allround lawn fungicide (don't use a product which is combined with fertilizer now that you just added fertilizer seperately). However, real control will not happen until the underlying conditions change, e.g. the soil dries out a bit (in WA, spring lawn disease is not uncommon due to wet winters).

In your area, fertilize your lawn in late spring, early fall and late fall. Avoid fertilizing too early in spring and do not fertilize during hot summer months. Mow grass high and mow frequently. cut grass 2.5-3.5" tall and recycle clippings to the lawn. If you water manually during hot summer months, try to water infrequently but deeply, eg. such as once per week for 2 hours rather than 15 minutes daily. The goal is to keep the soil consistently moist, but let the grass roots grow deep in search of moisture. also avoid the constant wet foiliage especially at the end of the day.

Lawn disease can often be diagnosed by looking at the individual grass blades at the edge of the circles. If they have hour-glass shaped lesions, have yellow, black, pink or orange spots or powder, or have black top or black roots, then it could be lawn disease. But irregular shaped dying grass which "spreads" in no particular pattern is often grubs. Especially in sunny areas.