Butternut squash leaves yellowing
OK, so I choose butternut squash as its supposed to be the least affected by the SVB. The plants have some along nicely and set about 6 fruit. Today I noticed that some of the leaves have begun to yellow. We've had the same hot weather as everyone else and have been watering every third day. Yesterday all the plants got a balanced granular fertilizer.
The picture is not the best but you should be able to see the issue.
Anyone have any idea about what's going on and what to do?