I'm cool fermenting a 1/2 ton of Chard in two stainless steel tanks,
using ICV-D254 and a temperature around 12 degrees Celsius (54F).
Inoculation was 4 days ago, and active fermentation began about 48
hours ago. I added 250ppm "Superfood" and 50ppm DAP at the onset, and
as of this morning everything smelled right. I'm using the same
program as I did last year, excellent fruit from the same farm, and
similar starting numbers pH3.31, TA 6.5 with 24 brix.

At about 2:00pm today, my wife phoned me at work and to brighten my
day with news that our cellar was beginning to smell like rotten eggs.

When I got home, the smell wasn't terrible, but it was unmistakably
H2S. I tested the must sugar and it was at 17.5 B. I then added
100ppm DAP, stirred very well and put the lids back on the tanks.
Samples from each of the tank smell and taste fine - no H2S.

Did I nip this in the bud? Will my yeast now use free Nitrogen rather
than sulphurous amino acids?

I'm hoping to enjoy my weekend, so any advice in advance would be most
appreciated.

P.S. my nutrient guide will direct me to add a further 50ppm DAP and
100ppm Superfood when the brix reaches 12.