Okay, when you say you made a lot of poisons do you mean lots of the same reagent/potion whatever or different ones? If it was different ones are they the ones listed in your spellbook for the spells you want to and can cast? If it's lots of the same ingredient you need usually more than one to cast spells. Or you can get Squinge's mod to enable witches to cast any and all spells without needing to use reagents. It's in his section here on Insim.
Hope that helps.

Brilliant, thanks very much