What vegetables are you referring too?
Sometimes the garden just grows slower than we would like!
Proper care, watering, sunlight, temperatures and weeding all play a part in the success of the garden. Some things we can control many be cannot.
I do like to give my vegetable garden a little boost with Epsom Salt.
I actually just add about 1/8 cup of Epsom Salt sprinkled around the base of my plants weekly and water in.
You also can mix it into a watering can and sprinkle unto the garden plants.
Here is a link with more information.