New tank

I got my new 75 planted 3 weeks ago and all appeared fine 
until today. Anyway I use tetra tablets in the substrate,
and Flourish fertilizers. The water parameters are as follows
gh=7 dgh
kh=4 dkh
I use 2 175 watt halides, 250 watt cable heat, yeast Co2,
and a trickle filter. Temp is at 80 degrees.
Anyway my contortion (?) val has turned greyish and will
probably be removed and some of my other plants have yelow
spots. Do you think this is due to a nitrogen deficiency or
is something else wrong. One other thing there is a whith
thread like (fungus ? ) stuff growing on a piece of 
driftwood. Any help will be greatly appreciated. TIA :-) .