It's either of 3 things ...
It's either a chemical that's gotten into or on the wood from your shop or where is was sourced.
It's possible the lines and compressor are contaminated with oil or moisture. Install a dryer and vapor filter at the end of the line as close to the gun as possible. A "giant" compressor sounds like it may have some maintenance issues...? Spray some clean white butcher paper to see if there is any discoloration with clear solvents in the same environment as you normally use.... temperature, fans running etc.
It could be the chemicals and ratios you are using are not appropriate or compatible with one another. Your spray pressure may be too high.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)