Struggling with CSV and multiple inputs

General
6

This you cannot solve with the join/batch node, this is about your input. (well maybe you could, but it is error prone)
How is your input processed, do you (want to) receive each a value every 5 seconds ?

I would suggest to set it up in a different way:

Date,Time,Measurement,Value
2020-04-27,00:10:03,Effluent_Out_PH,7.1
2020-04-27,00:10:04,Chrome_Redox_ORP,7.2
...