Oh no, the way the stat boosting works is.. Let's say you add 1 brown spice. All the following stats will recieve a random boost of any number from -2 to +2. [Farming, Fishing, Firemaking, Herblore, Mining and Woodcutting] If you add 2 brown spices, it can go from -4 to +4, and 3 spices, -6 to +6. If you add other color spices, you'll just affect more skills of the other categories.