Every basic recipe I find online included, Epsom, EO, Baking Soda, and coloring, but my batches are hard as a rock the next day! What am I doing wrong? I have a show next weekend so I can't order anything online. Should I not use the baking soda? Also, I live in the South so is it possible that the humidity is causing this (and it's very low right now)? I should also note that I am trying to keep it all natural. I appreciate any help you can give! Thanks, Tina