i think they need a nutrient boost. are they planted in potting soil?

I haven't had that problem. I transplant mine into 4" and larger pots and start watering with fertilizer water. All of my fertilizer water is 1/2 strength or weaker. I water them whenever they look wilty. I would rather water more often with weaker fertilizer than to fertilize 1x-2x per season. Mine keep very dark green leaves.

Yes a mix of 3 parts compost 3part peat 1 part vermiculite
half cup lime to mellow the peat and 2 cups base mix of
blood meal, bonemeal, greensand.
I think they have exhausted the nutrients as it has been
so windy I have had to water much more then normal and have
depleted the mix. I will try a foilar feed of liquid fish and kelp to see if this helps.
Thanks, PP

Foliar feed helps a bit, but not much in my opinion. I would use a higher concentration of fish/kelp and water the plants well with it. Do it once a week until you get them in the ground. Don't worry about over-feeding, they are tomatoes!
Also, make sure you're not watering bone dry soil or you'll lose all the liquid to the floor.