Record: Date, room, tray positions, flush number, symptom description, recent changes, trap counts.
Photograph the affected patch and one clean patch in the same room.
Write which trays and which part of the room are affected.
Write the flush number and the day count since venting.
List every change made on the farm in the previous three days.
Send all of it to your KVK or ICAR-DMR before buying anything.