Busy Lizzie in sensitive to warm temperatures- what is the temperature range at where you are?
It concerns me that the float is higher than it should be. Has it been always higher that the garden lid? If the soil is over watered, the cup will be filled with excess water and the roots don’t get enough air and start to rot and plant dies.
Please, take a look at the roots and let me know what colour they are.
Meanwhile, I would recommend to remove excess water from the tank and cup. Allow the plant pods to solidify for at least a few days. Then add some water and monitor plants, if new growth appears in a couple of weeks.