I can't keep my bromine level up in my 18X33 above ground pool. My water is clear, my alkalinity and ph are in the good range. I have a in line bromine feeder and have it on high, I also use borate and the levels are good for that as well. I heavily shocked it 48 hours ago and my bromine level is near zero this evening. I used 10 bags of good Chlorine shock and my levels was sky high but came down fast yesterday and today. I have no idea what is burning up my bromine nor how to correct it. I have had the pool 13 years and never had this issue. I did have some light brown dust stuff on the bottom of my pool but I have vacuumed it a few times and that is now gone. I really could use some easy helpfull suggestions.