Beginner Gardening: Zinnias have stopped growing after showing third leaves., 1 by Kalloused

Kalloused wrote:
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