Yellowing of watermelon leaves during the long rain season

The yellowing of leaves of watermelon plants is something farmers in the coastal region of east Africa Kenya are yet to identify the cause. The yellowing is more prevalent during the long rain season between march and june. The yellowing of the leaves usually begin after 3 weeks from the date of planting when the vine is about to begin flowering affecting yields and the overall health of the plant. No known cure is available. Surprisingly the yellowing does not affect vines planted during the sept- nov short rain season. This video was taken on june 2017