That looks to me like a bit of Early Blight which is a common problem in S.E. and Central Texas. I'm glad to hear you are already doing raised beds and drip line irrigation so that your plants aren't getting wet, just the soil, as that's hugely important when keeping funguses as bay. I also see (I think?) that you have removed some of the lower foliage which is good as well.
I do think you could do with a thicker application of mulch, maybe an inch or two of non-dyed pine bark mulch or, if you can find it, straw. When it rains, soil splashback onto the bottoms of leaves is how most Early Blight is transmitted. A little bit of EB won't cost you a harvest. You could probably remove some of the leaves that are completely affected, but you don't want to strip the plants of any more leaves than you have to.
Have you had heavy rains lately?
By the way, there is an OMRI organic fungal preventative you might look into called Exel LG. It's a soil drench that is supposed to prevent EB and other funguses and fruit rots. I used to use Daconil (chlorothalonil) in an Ortho Dial-n-Spray to prevent fungus, but now there are organic alternatives.