fusarium stem rot

Fusarium wilt is most prevalent in indoor gardens and greenhouses where it does happen outdoors. Reservoirs with nutrient solutions above 75° F (24° C) create a perfect condition for Fusarium to flourish to keep the reservoir cooled.
If water is an issue, then you will need to drain the reservoir and refill it with fresh water as well as nutrients. Fusarium wilt starts showing small spots on older lower leaves.
Interveinal chlorosis develops on the leaves very quickly