My other healthy looking plant.

It looks like these are planted in some sort of container: is that right? When did you plant them out? What growing medium are you using?

Are the wood pieces mulch, or part of the growing medium?

The growing medium is a mixture of 2 soils from my local nursery. Here are the descriptions:

Garden Mix Soil
This soil blend is ideal for a new garden. Lots of organic materials and nutrients makes it great for vegetable and flower gardens. This soil has a compost base and is blended with some sand. No green waste is used - less weeds & less problems!

Organic Garden Mix
Premium organic top soil containing fish meal, ultra-kelp, worm castings, alfalfa, composted fine bark, mushroom manure, and sourced low silt sand. Great for edible gardens and rejuvenating poor soils.

I bought half cubic yard of each and mixed the two for my garden this year. The wood is part of the medium as I did not add any mulch myself.

And yes, the tomatoes are in a container - 1 plant in each. I attached a picture of the planter. It is partially full of plastic bottles at the bottom (lined with landscape fabric) as I did not want to fill the entire planter with soil. I read Tiny Tims were good candidates for containers.

I transplanted them outside around the 2nd-3rd week of May.

They are situated on a south facing deck and gets sun for majority of the day.

Here is a link that might be useful:

They look fine to me. I would not worry too much.
Depending on the lighting and the camera, they look a bit on the pale side to me.
Have you been fertilizing them ?
I think they can use a round of a liquid fertilizer.
Some times no matter how good and rich a garden soil might be, it can be lacking certain nutrients.