These plants look quite healthy, although a bit "leggy" for my liking. Leggy plants are due to them not having enough light and being too close together. Light is one of the most limiting factors when growing tomato plants. Obviously temperature is important, but as long as you keep the frost away they will survive.
A minimum temperature of about 15 degrees is used in the commercial raising of tomato plants. Lower temperatures can affect setting of the flowers on the early trusses, but for the amateur grower, it will not be a problem as we tend to start our season later.
Here is an example of some really LEGGY plants that were left too long before transplanting.
The first thing I have done is to transplant my tomato plants into larger pots and space them out. The leaves should not be touching, so they get the best possible light. I have set them on trays so they will not root into the soil. I will add a small stake to each plant to support it while they thicken up. Normally, it is best to plant them into the soil when the first truss is in flower.
It is better to remove the seedling leaves as they have done their job, also any other damaged leaves, as this saves any diseases occurring. You can now really see how "leggy" the plants were that I purchased, especially the ones that were raised in blocks of six.
I also re-potted the chillies and peppers and you can see how much healthy root growth there is, but they were filling the small pots, so a good time to transplant them.
I have topped up my raised beds with some well rotted horse manure and some leaf mould that has been rotting down over the winter, this should give a good reserve of nutrients, although I will have to feed my plants weekly as the season progresses and the plants are full of fruit.
Lest year, I had great crop of strawberries that I grew in-between the tomato plants. I saved a lot of suckers from the plants and raised them in the polytunnel over winter. They are now ready to be planted back in the troughs or outside.