Huge difference.

I would suggest repoting immediately since you are already losing plants. Be as gentle as you can with the roots, keep them moist while out of the soil and try to do it in the evening so they don't have to deal with sun right way, but if plants are dying as is, rescue them.

Justaguy2,
Thanks for your advice; I won't make this mistake again! I'll definitely re-pot asap. I'm curious as to what the differences are between the two soils. I was hoping that this was just another marketing ploy -- package the same product two different ways and sell it as something different, which has been done frequently with other things.

As an EXTREMELY novice gardener, I bought containers, tomatoes, peppers and strawberries. I planted them in the containers by using Miracle Grow Organic gardening soil for veggies and flowers. Unfortunately, I didn't read the directions on the bag until afterwards...uh oh. This was four days ago. Is it worth doing over or is it okay because it is organic?? Please help.

Lots of gardeners get confused by the confusing packaging.

A commercial potting mix is typically made up of sphagnum peat moss some other stuff. A potting soil is typically made up of anything from sand, to top soil to sedge peat as a primary ingredient.

What makes the difference is the size of the particles in the mix. Small particles (like the size of actual soil particles) when placed into the confines of a container do not drain well and the end result is often a stunted plant that continually has to spend energy regrowing dead/rotted roots.

To get good drainage in a container requires using ingredients larger than what is found in the ground soil.

As to the question of 'uh oh, I just used soil, not mix, should I repot' it's a really difficult question for me to answer. If plants were just put in then yes . If they have established themselves and appear to be doing OK then probably not. If they are looking really unhealthy then yes even though they may die (they would die anyway so not much to lose by taking a risk).

In other words repotting (meaning removing the soil from the roots) is a huge stress on plants and for a few days will sharply limit their ability to take up water. If they were just potted it's probably not an issue, but if they have been in place for awhile it will be more of an issue. Exposure to sun/wind will take a pretty large toll on an established plant if it is bare rooted in warm, sunny weather because the act of transplanting removes super fine hair roots (you won't even see them) that do most of the water uptake for the plant.

If you would like more information on what makes a really healthy growing mix for plants I recommend this thread. It may be a bit late for this season, but it's well worth reading and learning the science behind container growing as it will make subsequent seasons much more successful.