pictures help, as well as posting specific water parameters.. such as but not limited to:
tank size: 50gal
how long established:
these things help, you can get as specific as you want (filtration,substrates/gravels,live/fake plants.. etc etc)
as for the white stringy poooopy my most educated guess would say it sounds like a digestive parasite.
as for the large white spot, sounds like a bacterial infection
pictures(if possible) would help members ID your sickness!