It probably has vermiculite or some other water retention crystals or somethjing in it, perlite would help with drainage but if its got something in it that holds water you will be having this problem the whole time.
Basicly your soil is the problem, next time you grow go to lowes or home depot get a bag of topsoil, a bag of composted manure, small bag of worm castings and a couple bags of perlite throw them all together then add either veg or flowering nutes and you got some damn good soil to grow in.