Quick! ArcGIS 10.3 Amateur needs help with mapping many unique values

Basically, we imported excel sheets for a pest in Virginia and the agent that was used to treat it. We have one excel sheet per agent and the categories are county and agent. We then joined each sheet separately to our already present county layer. Now we want to display which agent was used in which county. We decided to use Categories: Unique Values, Many. I then add in 2 Value Fields: Agent 1 and Agent 2 and then click add all values. However, only one of the agents shows up. The other one shows up as "Null". There are some null values in my attribute table, of counties that did not have treatment done, but I don't understand why this is showing up not the other agent...

Sorry if this is confusing, I'd be down to clarify, can anyone help if this makes sense?