The current climate dictates the relative humidity during the winter months, to be fair there’s not a lot we can do about it mine is currently also high at 89% and my masses are doing fine, a local grower / friend uses a de-humidifier during winter but I think thats an additional unnecessary electrical cost but thats his choice. I tend to hold back on watering and of course do not use my fogger/humidifier during winter, however I do open the greenhouse doors when outside temperatures are about 15ºc to allow good air exchange for a couple of hours a day.