Test the ph daily and try to stop the bounce back. (it probably will as the hardness was very high before) Don't make any changes over .2 a week or so. Hope your fish make it. And also, never try to lower the ph. It is very hard and unless in the hands of an expert, it will likely end in disaster (as you have already found out). Almost all soft water liking fish will live just fine in higher ph levels. Best of luck to you and your fish.
Ryan
Ryan