I don't think its a fungus. Because the buds and sugar leaf would be affected by this too, but they are healthy with no problems.

Seems they are just "borrowing" nutrition from the fan leafs.
MrGrowBig Reviewed by MrGrowBig on . Flowering clones turning brown. PLEASE HELP. What is your experience level? Novice/Experienced (I have done LOTS of research and reading, but not much hands on experience) Your medium: 1) Specific brand and type of soil? Fox Farm Ocean Forest with Fox Farm Happy Frog Fruit&Flower Top dressing. 2) Size of container? 3 and 7 Gallon (two sets of clones, a few are older than the others) Rating: 5