I have 3 little Carambola plants which sprouted in april. They are now about 3in height and are growing well until the mature leaflets start to wither and die...

So, the new leaflets grow well but die when then become mature...

Any idea of what could be the problem?

--> Temp. is from 73°F to 76°F

Is it too cold?

Humidity % is about 30% to 50%. Should it have more humidity? Or less...

Thank you anyone!!!