Hi @balaji27,
The discolouration on the leaf in your first image, where the surface of the leaf is yellow, and the veins remain green, is an indication of a condition called chlorosis. This happens when the plant cannot take up or use essential nutrients, most commonly iron, magnesium, or nitrogen. When the deficiency is mild, the yellowing may appear only between the leaf veins. When it becomes more severe, entire leaves can turn yellow, and growth slows.
Poor soil drainage, compacted soil, or consistently wet roots can trigger chlorosis because the plant is unable to absorb nutrients even if they are present in the soil. High soil pH can also lock nutrients out, especially iron. Environmental stress, such as cold soil, root damage, or overwatering, can make the symptoms more noticeable.
I would start by testing the pH of the soil to ensure it is in the right range, between about six and six and a half. If adjustments need to be made, then you can use How To Test And Adjust Your Soil Ph as a guide for balancing it.
Subsequently, you should assess whether the soil is draining adequately. If not, then aerating the soil with a garden fork and adding compost to improve soil structure and encourage beneficial insects will be worthwhile.
Once the soil is in the correct pH range and draining well, apply a slow-release all-purpose fertiliser such as Scotts Osmocote All Purpose Controlled Release Fertiliser. This will contain all the necessary elements to get your eggplant back to full health.
Check out How To Grow Eggplants for further guidance.
Let me know what you think and if you have further questions, please don't hesitate to ask.
Jacob
