Mixing henna powder with acidic liquid will give a oranger stain than mix with plain water.
Try to use only water in you mixes (instead of vinegar, tea, lemon juice) and let us know how will be the stain
How long have you been hennaing your hair?
Consider that for the first 4/5 applications, hair will have mainly copper tones, then going on with applications the color will became less copper and more mahogany.
After 2 year of henna applications, my virgin dark blonde hair went from a copper blonde color to an auburn brown (in the sunlight)/light mahogany (under cool lights).