Enchanting Table

I'm only getting 1 enchant at lvl 30 per items. Is this a bug? Im unable to fully test it but so far I've enchanted the following at lvl 30 2 Bows, a diamond sword, 2 diamond pickaxes. All items receive one enchant versus iron tools which received more than 2 enchants at lower levels. I can't find information whether its a bug or not.