Hi there mate I think you have overwatered but may also have the beginnings of a fungal disease called pythium which is caused from waterlogged or constantly wet soil. First way to combat this is to obviously stop watering so often and to prevent any nasties from continuing to thrive in the soil you should treat the soil. I like to use hydrogen peroxide @10mls/litre as a once off soil flush type treatment but as your soil is already to wet you will need to wait until it is dry before doing this treatment. 😀 Hope I have helped mate