Take the bags off to begin with as what you potted them in will hold water indefinitely and the last thing you need is more of it (I guarantee you'll see mold on the plant - Pg's are pomegranates, BTW - and air circulation is needed, not plastic. Secondly, get them into a decent amount of light for as many hours a day as possible (14-16). Once the top layer of your mix does seem to have dried, make a firm little scratch on the tree trunk and if the area under the bark is brown, or whitish, vs bright green, your tree is likely gone. However, if it's green (about halfway up the trunk), you can go ahead and repot in a much faster draining mix of grit (small sized aquarium gravel will do for now) and Perlite in about the same amounts, which would be 4/5 of the eventual mix, and after then adding some coarse, NON-peat based soil as the last 20%, you're ready to go. Vermiculite and peat won't allow the mix to breathe or to drain quickly - and don't let the pot sit in drain water either as roots rot that way, which will kill a tree very quickly if not changed. When water runs through a mix right away, then you can water as often as you feel the tree needs it without worrying about rotting roots, or mold. Bonsai are not house plants, shouldn't be in 'potting' soil that's mostly peat, and do need a more inorganic than organic mix to survive, plus they should only be watered when they need it (when at least the top layer is dry) rather than to a schedule of any kind.

Lucy, thanks for answering!
I already took off the plastic bag, as I saw mold on the plant.
I will look for acquarium gravel, but the reason I planted it into a regular mixture is only for rooting.
Can you, please, tell me what would be a better soil mixure in case I can't find acquarium gravel.
Thanks

If you want to root something, use perlite, and if you feel the need you can add a little peat moss, very well mixed, and the whole thing should be just barely moist (mixed really well to wet the peat, then squeezed out). Don't leave it in the sun. Any pet store will have the gravel and anything else I suggest would be harder to find.

Almost forgot - if you can, find a little brown bottle called "No Damp" at any garden ctre or even the hardware. A drop or two in the water of the mix will help keep fungus down.

Thanks, Lucy!

Another question: I just check the acquarium gravel at the store and they have different types, but all of them coloured and covered with some types of lacque (that is what sales person said). Is it safe for a plant to use coloured gravel? I assume it is as it is good enough for fish...
Thanks

It's safe, but they usually also carry a much smaller sized type that's like little chips of colored glass, not rounded, and they'll do a good job. I personally like the intermediate sized ones that look like (or are?) natural stone in various shades of sand, brown, tan, gold, etc.