Ill put in my 2 cents. Do not use weed and feed products. Always use fertilizer and weed treatments in separate applications. weed and feed products do not normally have enough nitrogen to feed your lawn for the month.

Not sure if this was the problem as I am pretty new to lawn care myself, so ill let the others give u more advice

Spread some fert in a perpendicular fashion to the line.

Create a schedule and alternate between:

a) cross left - right
b) cross up - down
c) cross - diagonally

All those are good suggestions.

If you want to get this back on track, it is a little too late for most of the US to use chemical fertilizers. Now would be a good time to learn more about the modern organic approach to lawn care. You can use a grain type fertilizer any day of the year, in almost any amount, with no fear of hurting anything. The only drawback is it takes 3 weeks to see the improvement. With your lawn the improvement will be as delicate as your supposed stripes you have now. Yes, I do see them, but jeeze Louise, talk about subtle!

This is what can happen to your lawn on a super organic regimen - meaning where most lawn nuts would apply 100 pounds of grain fertilizer per 1,000 square feet over the course of an entire season, this guy applied 1,800 pounds during the season. He was looking for the limit where enough is too much, but he never found it. Here's his lawn in July of 2010.

{{gwi:81154}}

Note the subtle difference between his lawn and his neighbor's lawns. The lawn is a mix of elite Kentucky bluegrasses. He was watering deeply once a week, mowing at the highest setting once a week, and fertilizing with 50 pounds per 1,000 of soybean meal and Milorganite ONCE A WEEK. If you want to do that, you're welcome. But all you really need is 20 pounds per 1,000 of alfalfa pellets (rabbit chow) once every other month. But if you want unmistakable results, you can apply more often. The first time you apply it will take 3 full weeks to see the improvement. After that it just remains deep green like that all the time unless you miss a drop.

Back to your lawn: In that condition it would be the best lawn on my block. Since you seem to be looking for perfection, let's ask some questions.

Where do you live?
What kind of grass is that?
What is your watering regimen? How often and how much do you apply?
How high/low do you mow and how often?
How often do you fertilize and what do you use?

Otherwise the lawn looks great.