NEED HELP STAT!

For the longest time my ph has been impossible to keeep up at 8.2 and we had to add buffer every day. we changed buffers and now the ph seems to be 8.6 or higher and doesnt seem to want to come down...
What should we use to lower the ph slightly???
Thanks Marc!!!

My hippo tang is changing colour. His black stripes are toning grey and back in seconds and he is flying around the tank. I did a water change today but he is the only fish acting strange. Any ideas ???