Boston Cucumbers wilting for no reason

[Crazy Plant Man]

This is the first year I've tried growing Boston Cucumbers, and up until this point, they had been growing incredibly well. I planted three plants that are all one foot apart on May 22. Over the past few days, they have been wilting for no reason. Today has been the worst day of all. I watered them with a watering can at the base of each plant a few hours ago and it didn't help at all. I gave them tomato tone slow release fertilizer a few days ago, so I don't know if that has helped yet. The most baffling thing of all is that it's only 80 degrees out, and earlier in the summer, the Cucumbers were thriving in 90 degree weather. Here are some pictures of the cucumbers:

The picture below shows the new growth of my middle plant, which is the first plant that started drooping.

This is the base of the middle plant. The other two bases look the same as this one. To me, it looks perfectly healthy.

 

[Chuck]

If they are like this at 7AM they would need water but if this picture was taken in the middle of the day I wouldn't worry. What does bother me is that white stuff on the buds in the middle picture and the dark discoloration on that small leaf. What does the back side of the leaf look like? When you water, water slow and deep. That soil looks pretty dry. Also when you water, water the surrounding soil too, not just the base of the plant as cucs send out widespread feeder roots

 

[Crazy Plant Man]

They were like this at about 11am, which is when I watered them. I took these pictures at about 1pm. I just felt the soil, and it was moist. It wasn't bone dry and it wasn't incredibly wet. I'm going to go ahead and water them again though.


This is what the bottom of the discolored leaf looks like.

All the other new growth looks like this, which is normal.

 

[Chuck]

They were like this at about 11am, which is when I watered them. I took these pictures at about 1pm. I just felt the soil, and it was moist. It wasn't bone dry and it wasn't incredibly wet. I'm going to go ahead and water them again though.


This is what the bottom of the discolored leaf looks like.
View attachment 13899


All the other new growth looks like this, which is normal.
View attachment 13900

On the topside of that leaf on the lower left corner it looks looks water soaked and that is one of the first stages of downy mildew. When you turned the leaf over it appear to have a grayish/whiteish color in that same area...IMO you are watering too little too often and your cucs are becoming infected with downy mildew
http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Cuc_Downy_Mar06.html

 

[Crazy Plant Man]

Should I cut off the part that is infected?

 

[Chuck]

Should I cut off the part that is infected?

Yes, but sterilize the instrument first and after every cut

 

[Crazy Plant Man]

Ok will do. Thanks for the help