Velutina

I suspect that they are not receiving enough light, especially for the size of pot they are in. Do the pots have drainage holes? Insufficient light + wet soil can lead to root rot. How long do the plants go between waterings?

I see you are in zone 6 so will have to overwinter the plants indoors. If you don't have a good area next to a window, you could consider getting some cheap fluorescent shop lights. E. ventricosum does very well under fluorescents (I've used NO and VHO bulbs, 5000-6500K)

For small bananas, I usually fertilize with miracle grow (but any liquid fertilizer will work). I just mix about 1/4-1/2 the recommended amount and move up to the full amount as the plant grows.

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Adam