Fertilizer - if the plants are in some kind of container, your fertilizer choices are a lot more important than if they are just in the ground. If they are in the ground, really any kind of fertilizer will be a benifit to your berry plants. For my blueberries, I use a generic 'balanced' 10-10-10 spread out around the base of the plant for about a foot just before leaf bloom in early spring, another application just before flowering in middle-late spring, and maybe one more around September for a boost of nutrients as they prepare to go into winter. I wouldn't worry about giving a new plant more leaves with high nitrogen, unless that plant is producing fruit at the time. In that case, you don't want the plant to produce lots of leaves, you want the plant to spend its energy making your crop. So don't fertilize it when it is blooming, or when the fruit is setting. If there is no fruit being produced, lush foilage is good for the plant.
Periodic use of compost is another boost to the plant if you take the time to make some. You will be pleased over time at the results if you use it. You can be pretty heavy handed with it, as opposed to the more concentrated chemical fertilizers.
watering - I think you will find that once they are established, a deep heavy soaking once a week to be less work and a lot more beneficial in the long run to your plants.
The circular brown spots could be just about anything. Insect bites, a symptom of some problem, not sure without a picture to refer to.
Bites in your leaves - pesticides kill offending bugs and beneficial ones alike. There may be times when its called for, but it should be a last resort. If insect problems are not widespread, and your plants are not being defoliated, try some of the various alternatives first. A good quick and cheap alternative is a mixture of soap and water sprayed directly on offensive insects. A good long term solution is planting specific repellant plants in the vicinity as a natural barrier to specific insects that are bothering your berry plants. There is loads of others. If all else fails, and you have to use an insecticide or loose the plant, then make sure to apply it sparingly and never when your plants are blooming.
Mulch is almost always good. It helps hold in moisture near the roots and acts as a weak natural fertilizer. Maybe an inch or two deep, out to about a foot or so from the base of the plant. It will also act to keep down weeds until your plants are large enough to beat down competition on their own, thus increasing the effectiveness of your watering and feeding.