When you say 24-D, you must have meant 2-4-D, which is a broadleaf herbicide, not a fertilizer. From the pics, I see a couple of nutsedge (a weed) and a lot of Bermuda grass. You can get rid of the nutsedge w/ an herbicidde like Sledgehammer. Getting rid of the Bermuda though is gonna be tough. You could mow your St. Augstine at the highest setting and that will shade out and slow the spread of the Bermuda. I'm not aware of any herbicide that will kill Bermuda w/o killing everything else in your yard. If you could take a picture that showed a wider shot of the lawn, that might be more helpful to get a sense of what you're up against.

Hello, I am new to St. Augustine and within the last week there been these spears that appear to be part of the grass itself. They, however, do not look right to me and my first inclination is WEEDS. Anyhow, they are everywhere in my front yard, but not in the back. The lawn is very sunny and there are no drainage issues. Pic attached. Can anyone identify or steer me in the right direction? Image link:

Should you? With the frequent rain this time of year, you may if you want to. It won't hurt anything, and can help stave off a fungal issue. That is good looking grass.

You may have had bugs. Something at the root it appears. There are several. Clemson and several schools publish articles on the grass care.