Gabe15

For now, just do not add anything but water to the soil. This will in effect slowly flush it out, but it would be a bad idea to completely oversaturate the soil while it is in such low temperatures in a not very active growth state, so you should wait to do that until it is warm, with lots of the sun, and the plant is growing fast. Your plant is very small, in a very small closed soil environment, nothing is being harvested, and so the nutrient demand is very very low, and anything it cannot take up will just sit in the soil and cause problems. Depending on the water you are using, it too could also be adding lots of salts which are causing problems.

This is one of the reasons I always use about 1/3 compost in my potting mix, it supplies plenty of slowly released nutrients, avoids the need for additional fertilizers which can easily lead to the problem you have encountered, and the organic matter in the soil aids in many other processes to help keep it a healthy, balanced system, even though they are just small containers.

The hyrdroponic fertilizers are typically very concentrated, and not meant for use in potted plants. Unless you were doing very precise application rate calculations based on the volume of soil and plant nutrient requirement (which is basically immeasurably low for your plant), you have very likely added way too much to the system.

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Growing bananas in Colorado, Washington, Hawaii since 2004. Commercial banana farmer, 200+ varieties.