Salon Tipping

I am new here, so please don't be mad if this topic was already discussed. I always tip 20% for my cut  If I get color on top of that it is 20% on the total for cut and color. The person shampooing me always gets $3 and a couple $'s more if she has conditioned me after the color and treatments, etc... Recently my stylist has had an assistant. She is the one who always shampoos me now and sometimes blows me out. I asked her if she was recently out of school or still in and she said she graduated several years ago, she just moved back in the area and is assisting right now. Why, I have no idea. I guess there is no openings at the salon? Do I still tip her the same as the shampoo girls or does she get more? She is only blowing me out sometimes and normal shampoo. Help! I feel that I am undertipping.