Does too much humidity stop or slow flowering/growth?

Short answer yes , with too much humidity your plants can no longer transpire and growth will come to a halt , ideal range for grow phase is 50/75 , and in flowering 40/55 , but you can take that with a grain of salt i have had humidity close to 80 % and they where just fine , just make sure you have enough ventilation and air movement to avoid mold issues. Peace