Hi Seburo,
You could try changing the text color, as MaDonna suggested; however, I added your theme to my browser to test the text. I wanted to see what you were seeing. Having done that I can see that you have your background color as light gray because the image you used isn’t wide enough to fit my screen resolution. Anyway, one good thing to always remember when choosing a background color is to pick a color that matches, or as close as you can get, to the background color of the image used. So my suggestion would be to change the background color to either the blue, rgba(0, 62, 124, 1), or the black ,rgba(0, 0, 0, 1).
Light background colors will produce a white drop shadow while dark background colors will produce a black drop shadow. Using a light background color, as you have, the system assumes that you are going to use a darker color for the text, thus a light drop shadow. But in your case, because you’re using a dark image you used a fairly light color text. And a light color text with a white drop shadow will look blurry, same if you have a darker color text with a dark drop shadow.
As for the text in the address bar, it looks fine because there is no drop shadow applied to it.
Below is a print screen of what your theme looks like on my computer.