A no! Each one of the foundations that you bought might be suited separately and on different occasions. Mixing all the products into a new custom foundation will ruin the exact tones, textures, and feel of each product on your face. A new product might react to your sensitive skin, even if the initials had not. The best solution is to fix a single foundation from a brand, perform an allergy patch test, and then stick to it/change it to find a new one until you have chosen the best foundation for your combination skin.