The picture of the pot is not as clear as I was hoping for. But, it does show there is no saucer under the pot and no water or soil on the table top. I can only conclude the pot soil is water logged or very soggy in the bottom of the pot.
Even tho you are using a 50/50 mix of potting soil & perlite its purpose is defeated with the non draining pot. ... The pot & soil MUST drain all free water out! Bananas (& many other plants) do not like their feet (roots) to be in water or stale water. And, soggy soil blocks air to the roots.
As
pjkfarm said above and I concur ... the pot is too wet ... This is the beginnings of root rot. ... It does little good to tell you the plant/pot is wet if we cant tell you why it was happening. Thus the need for full picture of the plant and pot.
Repotting is in order for the plant to survive.
- For an indoor banana plant, you need a saucer under the pot. Put a riser/spacer under the pot so the drain holes are above any water that drains out. Discard and water that drains; ... at least do not re-use to water the plant. You can leave the water in the saucer for humitity to the plant.
- If when watering, ... water doesn't drain from the bottom within a few seconds (20 or 30); then the potting mixture is not course enough. Add more perlite. A 25%/75% potting soil/perlite is good. ... I have & do used a fast draining soil mix in the bottom 1/3 of the pot with the corm sitting in course sand for the upper 2/3 of the pot. The corm neck/crown needs to be above the soil. Use course builders sand; pool filter sand; but do not use fine Play Sand.
- Trim off any black roots and soft black parts of the corm. Sterilizing the corm with household bleach water for a couple of minutes to kill any rot & fungus.
Fast draining means you pour water in the top of the pot and you see water running out the bottom immediately. You only want to wet the potting soil and not retain water between the soil particles like a sponge.
Good luck with you plant. ... OH the plant is lonely buy two more ... 3 is a party.