Question: Do you have any idea of what is happening to my tomato plants? They started out great and have set fruit but whole branches are turning yellow and it looks like it is spreading to other tomato plants as well. Carol
Answer: It looks to me like these plants are literally starving to death. I can’t tell for sure but the soil mix appears to have a lot of wood chips in it. This could be tying up your nitrogen and as a result starving your plants.
I would suggest starting a weekly foliar fertilizer program using Miracle Grow or something similar. I addition I’d apply about ¼ cup of a slow release fertilizer like Osmacote or Nutri Star per plant or if you prefer organics I’d suggest 2-3 Tbs. Blood meal and 1 Cup Cottonseed meal per plant.
Else plants are really suffering so I’d get right on it and then as soon as you can I’d suggest getting a soil test run to see what is going on with the soil.