I was looking at my hosts today, and found that all the daily credit values for my hosts were 0 for 12/30/2016 and earlier.
This made the charts completely worthless, which is what I was wanting to see.
Note: Around that time, I may have detached from BAM! and reattached, for each host, in order to remove "POEM@Home" from them.

So, what happened? Could it have been prevented? Is there any way to retrieve the data?

Hosts are:

1) d5802560f1ac3bbc04b7a6d53d92e796 -- 317619554
http://boincstats.com/en/stats/-1/host/detail/d5802560f1ac3bbc04b7a6d53d92e796
http://boincstats.com/en/stats/-1/host/detail/317619554/lastDays
http://boincstats.com/en/stats/-1/host/detail/317619554/charts

2) b7282f571425aa66d9dd355307864554 -- 317619623
http://boincstats.com/en/stats/-1/host/detail/b7282f571425aa66d9dd355307864554
http://boincstats.com/en/stats/-1/host/detail/317619623/lastDays
http://boincstats.com/en/stats/-1/host/detail/317619623/charts

3) 5213bdbbb4a2b3d7dbf379d21bdce83b -- 317619592
http://boincstats.com/en/stats/-1/host/detail/5213bdbbb4a2b3d7dbf379d21bdce83b
http://boincstats.com/en/stats/-1/host/detail/317619592/lastDays
http://boincstats.com/en/stats/-1/host/detail/317619592/charts

Regards,
Jacob

Host CPID change all the time and when they do their history is lost. No way to retrieve or merge it.

Dang! That's unfortunate, and not intuitive.
Thank you for responding, though.