Slimy spring onions.

Hi, I have recently tried growing my own spring onions.  Chopped off the rooted ends of shop bought ones. Planted them in general compost and popped on a shelf in the kitchen watered regularly.  They grew really well. Once at a decent size I chopped off leaving a couple of inches at the bulb to continue to grow.  When chopping them to use they felt a little slimy rather than crisp leaving a slimy residue. They looked fine. Could anyone offer me advice as to what this was. (First time ever growing any vegetable) thanks in advance.