What is the difference in the three I-N Serums? Can I use them all together? 

You can use them all or select any combination depending upon your skin needs as each has different key benefits.
1. PLANT RETINOL SCIENCE™ TIME TRAVELER SERUM™ fades age spots and stimulates cells. It contains retinol functioning plant ingredients and potent sea bioactives.
2. PLANT STEM CELL SCIENCE™ RENEWAL COMPLEX reduces lines and evens tone. It contains the highest level of plant stem cells in the line.
3. INTELLIMUNE SUPER SEED SCIENCE™ RENEWING OIL SERUM recovers and revives with plumping moisture and radiance. It contains the most concentrated level of our proprietary antioxidant-rich Intellimune Skin Complex.