Aww I hope your lemon balm survives. You just reminded me - my mint plant springs back as well. Also the bay leaf plant survives the winter too.
I also started with a plant from the supermarket. The mint is in a grow bag and the only thing I did was remove the dead sprigs and gave it water.
As I started composting 3 years ago and now have that wonderful dark liquid from the compost - I will add it to the thyme, rosemary, mint and bay leaf plants. I will investigate the use of this compost liquid as I have no idea about proportions. I hope to blog about this soon.
Regarding the cactus - when I see a baby plant shooting up - I remove it and re- pot it - nothing more.
Oh, that's easy!
I don't have a lot of cactussen.