We have had questions previously on aquaponics but it has been too difficult to figure it out as there is a very limited body of work on the phenotypic appearance of physiological stress in such systems. It could be that this is fungal due to the high humidity. I would suggest to rule that out you need to bring it to a lab.
As in previous cases my suggestion is to seek expert advice from industry suppliers of equipment or other growers who grow without soil

Good luck