I have had a garden for years and this year I built a 12x10 greenhouse to start plants in the spring and to grow Peppers and Tomatoes during the summer so far so good.
My peppers are Giant and just and are starting to get realy big peppers.
I had some black spots on the lower leaves of the Tomatoes I think mold I cut them off and sprayed with fungiside, looking good now.
All the plants get merical grow red once a week. the plants are in grow bags, the peppers are in 3 gallon 1/2 full and the tomatoes are in 5 gallon about 1/2 full.
My question is do I need more soil for the plants to grow in?
Welcome! 
IMO, yes, the plants need more soil. The containers should be filled to within 1 1/2 to 2 inches of the rim.
Tomatoes, especially, need plenty of soil, as they have large root systems. You can just add more soil on top of the soil that's already in the tomato containers, because new roots will readily sprout from the stem when it is covered with soil. I'm not sure if peppers do that, too, but another member will post soon and provide that information for you.
IMO, yes, the plants need more soil. The containers should be filled to within 1 1/2 to 2 inches of the rim.
Tomatoes, especially, need plenty of soil, as they have large root systems. You can just add more soil on top of the soil that's already in the tomato containers, because new roots will readily sprout from the stem when it is covered with soil. I'm not sure if peppers do that, too, but another member will post soon and provide that information for you.