Do you have ammo chips in your filter? Any new Ammo chips or if totally cleaned off, did you prime them in salt water? It's a long shot, sounds like you're getting it back under control.
On your test kit, is it new or old? Is there any expiration dates on the bottles? You know the importace of detail, if you doubt the results, document and do a new battery of tsts, remember to clean, rinse and get a good true water sample.
Are you on well or city water? I have a well and there are dramatic seasonal changes in the water due to snow/glacial melt, runoff, etc)