I picked up a Luster Leaf Rapitest Soil pH Meter and the soil in both pots is at about 6.0. Hops grow best in soil with a pH level between 6.0 and 7.5, so it is at the low end of what it should be. I drilled a few more holes in the bottom and sides of the pots and tested the moister level at various places and levels. The soil is still very moist in the lower half of both pots. I've left the irrigation system off since the weekend and there's no rain on the forecast, so I'll just continue to let the soil dry out for a few more days and see how the plants respond before watering or adding any additional nutrients.
On a good note, whatever the issue is, it hasn't appeared to really affect the growth of the main hop bines. The Cascade is once again nearing the top of the twine and the side arms on both plants are continuing to develop.