Are you trying to grow this Indoors?

Yes, I live in Britain, so the temperatures aren’t ideal or reliable outside.

Please don't use coffee beans or ground coffee, no matter if the ground product is used or unused. It's inappropriate for potted plants. What fertilizer did you purchase; in particular, what are the NPK %s? All fertilizers are not created as equals.

By the sound of things, the plant has likely been chronically over-watered. What did you use for soil when you potted up? If you potted up in pot size and were disappointed in the size of the root mass, smart money would be betting you're not going to be happy with the new direction the plant will be taking. I suggest you reassess your approach to growing. This Overview of Good Growing Practices will allow you to sidestep all the major issues you're likely to encounter on the trail to green thumb status, one of which is the soggy soil conditions currently limiting root function, or worse, wrecking root health. Good luck.

Al

Thank you so much for your answer! So do I just leave it to dry? I’m not sure what kind of soil I used, but it drains pretty well.
The fertilizer I’ve bought is ‘Miracle-Gro Mediterranean and Citrus Compost’, I couldn’t find the npk %, but the description is - “N/P/K, Nitrogen is used by plants for lots of leaf growth and good green color. Phosphorous is used by plants to help form new roots, make seeds, fruits, flowers and fight disease. Potassium helps plants make strong stems and keep growing fast. Additionally, there are 11 more minerals such as iron, iodine, fluoride, copper, zinc, chromium, selenium, manganese and molybdenum”. If it’s the wrong fertilizer, could you suggest a better one?
Also, I’ve read your article on potting, and should I pot back down or should I leave it?

If your medium is staying wet for a week or more, you can be sure it's holding enough excess water the water is, at a minimum, limiting root function and probably affecting root health by causing the finest roots (the ones that do the lion's share of the heavy lifting) to die/rot. The best way to resolve that issue is by developing a medium that holds little or no excess water. Because a medium like that will necessarily be made of a very large fraction of coarse materials, aeration and drainage will be innately superlative. Short of that, there are mechanical/passive ways to limit the amount of excess water ANY planting can hold; so, if making an appropriate medium is not in the cards, it would benefit the plant if you did a little study-up re how things like wicks, ballast, tipping the pot, or even simply holding small pots over the sink after a thorough watering and moving them up and down. Reversing the downward motion very sharply to upward motion uses Newton's First Law of Motion top expel excess water from the pot through the drain hole. An object in motion (water in the pot moving downward) tends to stay in motion (moving downward) unless acted on by another force ....... . On the reversal from downward to upward, water continues to move down while the pot moves out, so inertia of motion forces water out of the pot.

From the plant's perspective and for sake of its vitality, you should address the soggy soil issue somehow. Increasing the soil volume and pot size for a plant with an already unhealthy root system is probably not going to end well unless you are proactive about resolution.

Al

I'll make this simple for you lol, not a good choice for you there, indoors. I would look into something else. You will be struggling with it for the rest of it's life.

Thanks for all your advice! I’m going to refrain from watering until the soil is dryer, but I’ll spray water on the leaves so that it’s not completely dry.
I’ll let it out during the day when it’s sunny, but last time I did, the leaves started to wilt and never recovered.
Thank you for all the advice!! I really appreciate it.

I didn't answer further, hoping someone from Banana forum would. I see no one did, but I have to agree w/ Matt. I didn't want to discourage you, but Bananas are VERY tropical plants & therefore not good candidates to grow indoors, sorry.

You need to introduce it to outdoors slowly. It needs to be hardened off. Put it in a sheleptered spot for an hour or so to start with and gradually increase the time.

Okay, I’ll start introducing it slowly, is there any reason why the plant started declining? Because it was doing so well.

How us doing the plant now ? Is possible was a fungus . Do you know what type of Musa Bananaplant is it ? Where you live (Great Britain) outside you can grow year round the ornamental Musa Basjioo ! Cheers !

Old post, I know, but still, there is nothing in the OP's images to suggest there is a fungal pathogen at work. The symptoms were caused by cultural conditions in the pot that were stressful to the plant. The most likely cause was an excessive amount of water in the medium for an excessively long interval, or a badly compacted medium. These conditions limit roots' ability to function normally, making it difficult for the plant to move water to it's most distal parts - leaf tips and/or margins.

Al