No longer able to backup with Time Machine

I have backed up my 2.93 GHz 640 GB iMac with 4 GB of memory for years to a 1TB external drive via Time Machine. I'm using OS X version 10.7.5.  I've started to run out of space on the iMac so I got a 2TB external drive to move my photos to.  Before I did anything, I made sure I had multiple backups on both Time Machine and my cloud storage (Back Blaze).  I had backups going back over a year.  I moved my photos via Lightroom and have been able to create one successful backup but now I get an error message that there's not enough space on the 1TB to backup and only the one backup exists in Time Machine.  I've run a Disk Utility on the external backup drive and there are no issues.  I'm not understanding how all of a sudden I can no longer back up when I have the same amount of data, actually less since I deleted some duplicate files.  And all the old backups have disappeared.  I'm concerned that I only have one backup from last night.  It's as though that one backup is huge.  When I try to click on the folder to check the folder size, the drive keeps churning and never returns the file size.  Is this a sign of a corrupted or damaged drive? Any other options or troubleshooting?


Let's try to make this less confusing:
You have a 2TB external drive for storing photos. That drive is working fine.
You have a 1TB external drive for your TM backup. That's the drive with the error message that there's insufficient space on the drive.
Now, after deleting some duplicate files, the old backups have disappeared.
I understand that you have multiple backups of your data.
If you've made multiple copies, and have the data backed up on the Cloud, wouldn't you be able to copy the Cloud copy onto your 1TB external?
Is it possible that a prior TM backup has the data you need? Are there any error messages on the 1TB external? Is the drive new? (As you probably know, drives either go bad early, or last for years.)