Crypts will melt anyway when you put them in a new tank. Happens to everyone. Don't disturb, let them do their own thing. They are sensitive, but easy to care for, plants. The sulfur smell is most likely from the substrate where a lot of bacteria make gas, and that's released when you open up the substrate.
Check your water parameters. Probably need a couple of good pwc.
only change the water during a cycle to get your Nitrites or Nitrates back down to a readable level. A water change will not remove any BB from the tank, just the ammonia you added along with the bacteria byproducts (Nitrite, Nitrate). The sulphur smell is from what is going on in the substrate, it is the byproduct of anaerobic metabolism. What are you using for a substrate?