dehumidifiers work great and also good ventilation and circulation help. 80% is pretty high, but you won't have too much of a problem if you are in veg, if you are in flowering I would deal with this asap. You will get mold or bugs.
First of all is your RH of 80 in the clone, vegetative, state, or flowering state? If it is in the clone state then that would be fine. The last two states not fine at all. Did you notice this high humidity when the lights are off or on? My flowering room could get that high when the lights are off but I have a dehumidifier going on at intervals when the flowering lights are off.