David, thanks for the question.

It is a little hard to tell if this is septoria at this stage. Caution would say to remove the leaves. It is rather common for lower leaves to yellow due to shading, nutrient issues, et al. Fungicides, synthetic or organic are primarily protective. Many gardeners use these when conditions suggest the risk of infection. The best thing to do is monitor your plants regularly and get a jump on any problems.  Check out the following links:

• https://extension.umn.edu/plant-diseases/tomato-leaf-spot-diseases
• https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/fungal-spots/septoria-leaf-spot-of-tomato.aspx

I hope this is helpful.

David, thanks for the question.

It is a little hard to tell if this is septoria at this stage. Caution would say to remove the leaves. It is rather common for lower leaves to yellow due to shading, nutrient issues, et al. Fungicides, synthetic or organic are primarily protective. Many gardeners use these when conditions suggest the risk of infection. The best thing to do is monitor your plants regularly and get a jump on any problems.  Check out the following links:

• https://extension.umn.edu/plant-diseases/tomato-leaf-spot-diseases
• https://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/fungal-spots/septoria-leaf-spot-of-tomato.aspx

I hope this is helpful.