Tomato plant leaves going yellow with black markings. Flowers good. These are bush tomatoes in pots and have never had this happen before.
Tomato Plant Leaves Going Yellow
Certified GKH Gardening Expert
Generally when their are yellowing leaves it indicates a watering issue. Either to much or to little.
Container plants need daily water and even twice a day when temperatures are above 85 degrees.
Check to see if the soil is damp but not soggy.
If the plant roots are sitting in water this can lead to root rot and fungus problems.
You may want to treat the plant with Neem Oil as a precautionary measure.
Here is a link to possible issues.