black spots near roots and up stems

Question

My beautiful palm tree started showing black spots on the stems near the roots and then further up the stems as time progressed. Some of the leaves have a brown tinge to them. It hasn't stopped growing new stems/leaves. I cleaned the stems with soapy water and most of the spots disappeared but now they are reappearing faster than ever. Leaves are starting to die off at the ends. The only thing I haven't done is change the soil totally - I'm scared that it will die if I disturb it too much. Any advice appreciated.