Q.Yellowing tomato plants
This tomato plant just started yellowing from the inside of the main stem outward. I suspect a mineral deficiency, but have been feeding it weekly using Miracle Grow since planting it (grown from seed started in our basement in February). It is planted in an area of our garden that has a lot of peat moss, and very little soil mixed in. Could you advise how best to treat this issue?
How is your watering scheduled?
Make sure your giving a deep root water, as shallow watering can leave the growing root system thirsty.
Inspect your plants carefully, look for signs of insects or damage.
I personally would cut back on the fertilizer. Once a week should be sufficient. You don't want to grow a plant, you want tomatoes!
I love to use Epsom Salt on my tomato plants. You can mix in water or when I'm busy I just sprinkle about an 1/8 cup around the base of each plant.
Here are a couple of links I recommend reading.