i use Scotts Osmocote for gardens and fish fertilizer. I did use ironite on the start (since I used a lot fo the cheap topsoil from the store - sand and mulch). This combo is good. won't burn the plants and the fish stuff is a good booster too.
I wouldn't trim them, no matter what. If you trim them and some bug bites off the head of the vine that were left then the plant may be stressed. With several of them growing, you know the chances are good at least one will make it.
So far only one vine was eaten by a bug so far. The other vines from the rhizome are doing great. I use the organic slug killer and neem oil to kill the bugs. Even then some bugs will be left. Don't take a chance. I will not use anything stronger (maybe seven dust) due to other veggie plants in my garden (tomatos, peppers, melons, etc).
More leaves, the more energy is going to the plant.