You can't keep all the hops happy all of the time

My Cascade is not very happy at all. It has stopped producing new cones altogether. There are still a few left on it that I hope will continue to mature. The weird thing is that the plant doesn't appear to be suffering that much, particularly in comparison to the Willamette beside it (on the left):

As you may be able to see, the Willamette is producing a huge number of cones despite not looking very happy. I have found a few dead and withered shoot tips on the Cascade recently though:

We have had something of a dry spell recently. It's quite possible I was not fastidious enough about keeping them watered. As neither the Columbus nor Willamette are showing similar symptoms, I wonder if my Cascade is just more sensitive to drying out. The cones that are left on the Cascade still look healthy (even if those particular leaves have been attacked slightly):

There is new growth on the Cascade, so I'm hopeful that it will make a full recovery:

The Columbus is going nuts in comparison, with new cones forming all the time while the older ones continue to mature (looking forward to harvesting more):

In the last few days we have of course had a good amount of rain. I think I will need to make a concerted effort to keep an eye on how much rain we're getting and water accordingly.