Question, (I have similar spots) if the CH did get high over the winter and formed these white blotches, how do you get them off?
I have a TF-100, and yes I dropped my TA quite a bit in the last few months as part of a test and it has worked.
I have a rather lager spill way from spa to pool and the aeration was causing pH to climb daily and I was having to add acid all the time. I dropped the TA down so see if it would help with the higher PH, and PH rise seems to have slowed, only have to add acid every second or third day and only 12 oz at a time instead of half a gallon every day.
I think I figured this out finally, pics to white spots below.
http://s1026.photobucket.com/user/badag98/library/
Numbers from Yesterday:
FC- 5.5
PH: 7.6
CYA: 60
TA: 90
CH: 225