Hi and welcome to the forum
Is the soil a proper aquarium plant substrate or soil from a normal terrestrial garden potting mix?
If it's from a garden potting mix, remove it and wash the tank out and set it back up.
Aquarium plant substrates are not worth having and regularly produce heaps of ammonia for months after its added, and this stops you having fish in the tank until its cleared.
If you want a plant tank, just use brown gravel and a liquid iron based aquarium plant fertiliser.
As for the current issue, you can try draining the tank and refilling it with dechlorinated water. Try not to disturb the substrate when you do this and see if it helps. Some people put a bowl in the aquarium and sit it on the substrate, then slowly fill the bowl with water and let it overflow into the tank. This can reduce the amount of substrate being disturbed when adding water to the tank.