After teardown, battery suddenly needs to be replaced

Hi,

I opened up my laptop and successfully replaced the keyboard (thanks iFixit!) Everything is better now except that it's now telling me the battery needs to be replaced. It seems to be losing its charge slightly faster than it was, but not a big difference yet. However the condition is listed as "Replace now." There was no such problem before I took it apart.

So I'm wondering if I did something wrong, if something is messed up inside, is it a result of plugging and unplugging the battery, or is it normal?