Your node must have gotten to the point where it's now validating everything in the new blocks that it download from its peers after reaching its version's default "
assumedvalid" block.
But 0.05% per hour is tad too slow, are you using an HDD?
If so, don't rely on the estimation too much since it's tend to underestimate the speed specially with slow disk and low dbcache.
What are your settings and specs?
i installed bitcoin core on this external hdd rather than setting the datadir to it. would that have mattered here?
The binary's directory doesn't affect your overall sync speed.
What matters is if you've put the datadir in that external HDD as well, if so, that's also contributing to the issue.