Problems appending lines from a script

I'm writing a script and here's how i'm inputting into the CurrentOutput.csv file.

echo "$col1,$col2" >> CurrentOutput.csv 

Input.txt

1.2.3.4
2.3.4.5
3.4.5.6

CurrentOutput.csv

1.2.3.4
,DNS1
2.3.4.5
,DNS2
3.4.5.6
,DNS3

DesiredOutput.csv

1.2.3.4,DNS1
2.3.4.5,DNS2
3.4.5.6,DNS3

I've tried echo -e "$col1,$col2\c" and echo -n "$col1,$col2". Is it because I'm writing from a .txt file to a .csv file? What am I missing here?