Zinnias have stopped growing after showing third leaves.

Hi!
This is my second year growing. Last year everything came out great so I added more variety this year to try something new but am having a problem.
My four O'clocks and Johnny Jump Up's have come back(the Johnny Jump ups are already in bloom) and I used some Jiffy Peat Pods to start some Zinnias,MoonFlower Vines(first time trying and is doing well so far,about 12 inches long wrapping nicely around it's rod),Sunflowers(also not growing but not dying,same as Zinnias but I suspect not enough sun),Cosmos which are growing wonderfully and some Zinnias.

I used peat last year and not these peat pots so I am new to them. I improvised and sifted through the bark and used plain potting soil to sprout my seeds and everything grew fine. The directions said to plant "Pot and All" which I did....but (almost)all of the flowers wouldn't grow until I dug them up and peeled the peat away and loosened the soil around it. The problem has been with the Zinnias, the haven't made any new growth since moving them outside. I have 2 each in two 14 inch pots and 2 in the ground and they are very healthy(green moist leaves,no yellow).....they just won't grow. They look exactly like they did when I took them out of the peat pots. I'm baffled and am almost a month behind on growth.
Does anyone have any idea what is wrong and how I can get my flower sprouts out of this "Stasis"??
I'm In Utah County,Utah.
Thanks for any help!
Kall

Hi Kall,

I have zinnia seedlings that aren't doing very much either. They are about the same size as yours. To be honest, all my seedlings are slow growing this year. I'm in zone 5a and the weather here has been cool, rainy and not a lot of sun for quite awhile. And I think that's EXACTLY the problem. Zinnias love sun and heat as do many other flowers. I'm hoping when summer finally kicks in, they will all start to take off!

Thanks for the response PaGirl!
That actually makes a lot of sense. We have been having some unusual temps here in Utah and I think you might be right. Although it has finally started getting in the mid to upper 80's and sunny during the day here, the temp will drop into the mid 50's at night(very, very cool for Utah this time of year) It looks like I will have to show some patience and hope we have a long lasting summer so I can get these flowers to bloom. Thanks for your reply :)

Zinnias and pretty much everything you list are plants that really need the heat. You might try putting a row cover over them, or individual covers to try to conserve heat. If they are in containers, then move the containers to the warmest location. You might need to move them again when summer really gets here.

Thank you Diana, that is what I have been trying to do. Most of my flower seedlings are in pots and I move them in accordance with the sun so they can stay hot as possible. I will try to construct some sort of cover for them until it starts getting hotter at night. I just noticed today that my Moonflower vine has come to a standstill over the past few days, so other than the Violas and Cosmos everything is in stasis for the moment. Thanks for the reply and hopefully it will get warmer during the nights soon.
Kall