Can you post a picture of the weed seeding activity?

The first of a few photos to come is attached. I mowed about 24 hours before these photos were taken. Before mowing, I snipped several dozen tall seed heads off the dallisgrass to prevent broadcasting the seeds. During mowing, I probably mulched another dozen or so that I had missed. What's in the lawn now are likely younger than 24 hours old.

What I noticed last summer--my first season in the house--was that the seeds became apparent, it seems, only when the dallisgrass stalk shot higher than a couple of inches tall. These are growing prostrate, making the ability to trim them before mowing problematic.

I don't think these seed heads are necessarily unusual. I just think the timing of my first nitrogen application a week or so before their sudden (and prolific) emergence may be more than just a coincidence.

Another photo.

And another.

"regularly mowing very low"

I know you said you regularly mow very low, but in the pictures it looks like you haven't mowed in a while.

The fertilizer will make everything grow faster including the weeds, which will form seeds if you let it grow too high as you have noticed.

You need to be mowing twice a week or so depending on how short you are really mowing. This will cause your bermuda to want to grow horizontal instead of vertical and can choke out most weeds. Also, most weeds (not all) don't like being cut short often, which can kill them off eventually.

How short and how often are you really mowing?

" I mowed about 24 hours before these photos were taken"

I just noticed you said you mowed 24 hours before the photos were taken. In that case it doesn't look like you're mowing very low.

Bermuda likes to be cut very short. Anywhere from well under an inch to 1.25 inches.

I keep my front lawn under an inch with a manual reel mower and about 1.25 in the back with a rotary mower.

How low are you mowing?

I have my mower set to the next to lowest deck setting. I can't set it at the lowest setting, as my yard isn't level enough to pull it off. I mow twice a week, typically.

This last week was an exception, since we had many days of rain that prevented me from mowing for nearly a week. In the mow before these photos were taken, I had the deck set on the third-from-lowest setting, as to not take off too much at once.

Sounds like you're doing what you can, then.

I'm pretty sure I've had that weed in your pictures in my lawn before and it had seeds even though it was cut very short. It was all growing outwards horizontally, which is how it avoided the lawnmower blades. I only had a few and pulled them easily.

If you don't have too many maybe you can pull them.

Also, just to clarify, my statement about cutting height is for hybrid bermuda. I get the feeling you may have common bermuda, which should not be cut as short as hybrid, but I'm not sure how short. You can find the info easily by searching.