Week 2 (left) week 1 (right) of flowering. Tempera...

higher humidity can bring risk... but, your VPD should be good. raising humidity is one tool for combatting higher temperatures. unfortunately, the solution will probably reduce teh effectiveness of your cooler, which will raise teh temp a bit. Greater exhaust or air echange would lower the humidity. running a dehumidifier, lol funny for this context, would raise temps even more. (depending on size of room, those are upto another 400-500watts too for a 50-70pt dehum. 60 RH isn't too bad, but you are right on the edge. So, maybe run the cooler a little less and accept a a little extra heat... if plant still looks healthy, it's no big deal. some plants won't be the slightest bothered at 30C, for example. Good circulation and air exchange will reduce risk while the RH is near that 65+ zone. If plants get a bit too lush, you may need to dilute your fertilization 5-10% more than normal.. .this will offset the increased transpiration at leaves which leads to heavier drinking... the plant's metabolism doesn't change, but you are feeding more per 24 hours, so, it may require a slight adjustment down, if you observe a reason to do so.. don't delay. only other option is to ditch the evaporative cooler and use a portable AC or your home's AC a bit more. Play with exhaust/air exchange a bit? you havev a small problem, so a small adjustment might be enough too.