Tomato plants are scrawny, but setting fruit

[Greenhousesalsa]

I am raising tomatoes in containers, in a greenhouse.
I have both determinate and indeterminate plants.
After much research, I cut down on the amount of nitrogen and added Epsom salts to the soil. The plants are green, have a lot of flowers and in most cases, are setting fruit. However, the plants look scrawny. Some of them don't have a lot of foliage.
Should I add nitrogen?
We have had record heat here lately (7000 ft. NE Ariz) and have been struggling to keep the temperature under 90, using the exhaust fan and misters.
It is now cooling off and getting into it's normal temp. range for here.
Is heat the issue, not enough nitrogen or water?
Thanks for any advice!

[Lindsaylew82]

Let's see your plants!

Pictures are so helpful in determining some of the problem you may be having!

Add some pictures of the area you have them, the plants themselves, the container in which they are growing, etc.

Offer us more information, what varieties of tomatoes are they?

What size pots?

[imafan26]

What size pots are they in?
If the flowers are not dropping, heat should not be an issue. However, in very hot areas it helps to plant heat resistant tomatoes. What variety do you have?
What did you put in your pots. Potting soil? What kind. How much fertilizer and what kind. Epsom salts provide magnesium.

Tomatoes are heavy feeders and require adequate nitrogen during their growth phase. You just don't want too much nitrogen so that you will get foliage at the expense of fruiting. Since the tomatoes are flowering a side dressing of fertilizer is fine.
If you are not organic any fertilizer with numbers under 10 will do. I use citrus food (6-4-6) for everything but I get tomato food when it is on sale it has an npk of 9-12-12. I use 2 tablespoons for an 18 gallon pot.

If you want to be organic you can use tomato tone or vegetable tone. You would have to use about 1/4 cup. I would also add a tablespoon of blood meal for faster nitrogen.

[Greenhousesalsa]

They are in 5-6 gallon nursery containers, about 18 inches in diameter.
Using Kellogg's container potting mix. Get lots of mushrooms if I over-water.
In 12x16 greenhouse with exhaust fan on thermostat.
Used misters several times recently as the temps crept up to and over 100.
Summer rains coming now, so daytime temps will be in 80's, nights in 50's.
Seeds came from Tomato Growers in Florida and Territorial Seed in Oregon. Discussed growing circumstances with them prior to ordering. All heat resistant.
2 are indeterminate, the rest are determinate.
Plants look fairly good. Green. For the most part not dropping flowers. They are just skimpy.
Did soil test and very little nitrogen in soil. PH is neutral.
Think I will try adding some nitrogen.
Thanks for your help. Need all I can get. Tried to upload pictures. I couldn't get it to work.

[Lindsaylew82]

Haha! Nitrogen helps! Best of luck with your crop!

[TomatoGirl]

I grow my tomatoes in the same size pots. Compared to the same plants in my friends gardens (I gave them some of my seedlings) they do have a lot less foliage. BUT, they are extremely healthy, lots of flowers and fruit. I think it is just to be expected when growing in small containers. They just don't have the root space to grow in to huge plants.