I have had this issue for several years. Finally while getting our hot tub repaired the repairman told us that our tub needed to be shocked once a month cause the bacteria build up can cause infections in women. Funny thing was we made no mention to him about my problem. We have a well and apparently the well water not being treated initially like municiple water systems has a lot of bacteria. Combine that with the heat of the tub...prime breading grounds. So we did this and 90% of the time I do not have a relapse. Only when we have not balanced the tub properly do I have a reoccurence. To cure it I have used all the above you have mentioned. Sometimes it helps and sometimes it does not.