Im a first year grower myself and have a Japanese beetle problem here in NC. In my opinion, the hanging bag traps are garbage. Didnt help me a bit. I suggest looking for the source of the beetles. I found the source of the beetles on nearby grapes and killed them there with safe pesticides. There must have been a hundred of them in a 2 square foot area and 70% of them were making babies. If you cant find the source,I suggest putting up traps around the garden. That way the beetles get the trap first. Thats what I have read works.
After finding the source,I went from 30+ beetles destroying 3 hop plants to less than 10 beetles on 2 plants. Now I just hit the plants a couple of times a day to get the beetles off. They suck at flying, especially in the morning, so thats the time to do it. If you can grab them, kill them.
I had a similiar problem with my plants in terms of the bottom leaves and began a miracle grow regimen-once a week. I also bought manure and topsoil and added a large amount to the base of every hop plant-once a month. If that doesnt do it than watering or heat might be the issue. I didnt change my watering habits though and the heat here is not so intense so I cant help you there. Wish I could.