The dehumidifier will give off too much heat inside a tent. The problem is that all air that's being pulled into the tent is 88 - 90 % - as soon as you dehumidify it, it's being replaced with humid air.
If your RH is that high then you aren't exhausting enough air. It's 100% humidity here today. When my light is on the tent is about 38% with no dehumidifier. Dehumidifiers just cost significant amounts of electricity and add heat to the space.
You have the air sitting in the tent too long picking up moisture from the plants and water. If you had a proper sized exhaust fan setup pumping the hot tent air outside it would dump that moist air before it could elevate the humidity to that level. Mine only goes up to about 59% at night.