Help please ! 2 plants are fine the third one is struggling

[T_BrosFarm]

Hi everyone,

I have 4 plants, Three of them are doing fine and have no problem but the fourth one is not doing well. Started when the first single bladed leaves started yellowing so I cut them but now my two biggest leaves are also not doing well.

They all had the same watering and nutrients so I am really confused now.

Also my air filter has become all rusty and the cloth all around it gradually has become all white with dust and the lower section has become all rusty.

Any input would be greatly appreciated.

 

[TripsRabbit]

Some plants are magnesium sensitive and will get a calcium lockout with normal amounts of calmag given. Other plants are just calcium or magnesium hungry. For that reason I like using epsom salts and garden gypsum for magnesium and calcium. If I get a plant that gets an early calcium or magnesium deficiency I can just sprinkle a handful of one or the other on top of my coco and stop the progression of the leaf damage before flip.

 

[TripsRabbit]

The petioles aren't red so I'd say calcium defiency.

 

[Aqua Man]

The petioles aren't red so I'd say calcium defiency

Agree... thinking over watering is the cause.

The filter is a result of high humidity. Carbon filters don't work well over 70%RH if they are quality and lower if they are cheap. Looks like that one may need to be dried out well before use if it hasn't already been.