Fortune Enchantment

I have a chanted a diamond pickaxe with Fortune 3 After that I tried to mine diamond and only got one for every three blocks I mind and then after that I mind Redstone with the fortune 3 pickaxe and only got four or 5 and I mind Redstone with an iron pickaxe and got the same results 5 or 4 Redstone 4 block.in the image I have attached it shows I only got two Cole from 2 coal blocks while mining it with a fortune 3 pickaxe.