People say that its nute overdose, deficiency, pH etc etc this is no help, you need to take one action and see the results before considering it to be somthing else! I am sure that on your next grow just 10 percent perlite would help instead of 50 percent or what ever it is. Drying soil in two days is bad for the plant as well. You probably won't solve the problem here before harvest but you may slow it down. I can only think your grow is set up wrong, soil drying in two days can cause burns, wilting, nute lock and a whole host of other problems. My best advice is to try save these plants the best you can and to get them to finish, then work on some cultural practises for the next grow like the right soil mix that wont dry after two days, proper watering once or so a week and a proper fertilizer schedule that will not over or under toxify your bud. If there a no roots popping out the bottom of the pot id say the plant still has some nutes left in the soil before it needs fertilizing. Have you considored that perlite holds water and nutes within its honeycomb structure and this may be the problem even though someone said it was ok, also too much perlite and when you water the perlite floats and breaks the root hairs. You have a few ideas to try to save this plant but overall a good learning experience for the next grow where i strongly advise you to change almost everything and start the right way. Im sure you can finish the bud on the plants and would be tempted to just go with straight water for the next few days. My best diagnosis is maybe root problems from the perlite and ferts but anything i say here is a guess so look to the next grow and good luck. Keep us posted with what you are doing and pics of the results, will try to be more helpfull as time goes by. Good luck