I'm thinking the steer manure may be the culprit. The salts present in steer manure could lead to similar problems to what you have pictured. While steer manure can be an okay input, you should go easy with it. Try dumping a pile on the lawn--you'll see that it can burn the grass, so same is true for hops. If chicken manure is available, I'd argue that it's a better choice. The good news is that the problem may correct itself as the salts leach out through watering. Maybe a good deep soaking is in order.
Note that if these affected leaves are mainly on the lower regions (say the first two meters) then I wouldn't worry about it too much. Same goes for the aphids, the pants can handle some pests. In fact spraying down the plants too much can lead to problems, like mildew and sunburn, in particular climates.