You balance charged it to 100%, but I wonder if that charger didn't think it was a 1s or 2s or something and only charged it partially. Because that's whst it sounds like. Do you have a multi-meter? If so, you can check the cell voltages with one.
That LiPo checker is ok, but you can get the Cellmeter 8 for $3 more, and it is also a servo tester. So if it were me, I'd cancel that order and get the Cellmeter 8 instead.
But I would still get a LiPo alarm to use til you make sure your LVC is working correctly.
What is the voltage of the battery? If it is above 9v, you should be ok. If not, you're going to have to bring it back above 3v/cell in nimh mode more than likely. If it is overdischarged, the battery likely sustained some damage. I am not familiar with that charger, but looking at the specs, I...