white residue on my plants and tray table

i opened my flowering space today and discovered a white residue on the tray table and some other layers or gunk. i think it's from the nutrients and CO2 but i'm not certain. any ideas?

any pics? could be a salt build up from your nutes like you said. mildew can occur and it is a white powdery substance, i would look into this as well because i dont think that nutes can build up so much that it leaves a residue on the plants, but i am not 100 percent sure.