Blackdog40,
I doubt the changes you saw were a result of lake turnover. If spring turnover were to occur, it would do so when the surface temperature reached 39F and we've been past that a long time!
Globs of 'moss' floating around can be the result of algae that covers rocks and other substrates being dislodged by either inflow or wind or simply aging/maturing enough that it cuts loose from the substrate and floats around. Some algaes becoming 'bubbly' with the oxygen they produce which causes them to float to the surface.
Green water would likely be the result of an phytoplankton bloom. Not all blooms are bad. I haven't seen the lake first hand so I can't say for certain. With our warmer than normal water temperatures this year a few of my lakes are greener than usual for this time of the year.