[M. Bland]

Hello,
I planted some Savoy cabbages this year. I live in a pre-alpes area in France close to the Savoie department, so I thought Savoy cabbages would cope with the cold.
I have just cut one open and there are small brown bits through a lot of the leaves - no sign of any pest - and the rest of the cabbage is fine.
I looked online and found an American site which states
"Problem: Tipburn
Affected Area: Leaf
Description: Although symptoms are not visual from the outside of plant, the edges of leaves on the inside are brown. Necrosis may occur only along the margin or along the whole edge of the leaf.
Control: The best forms of control include applying nitrogen in nitrate (NO3 -) forms rather than ammonium (NH4+) to fertilize, avoid water stress, and have good irrigation practices."
Also I found http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_Nonpathogenic.htm
which gives more information.
This looks the closest to what is wrong with my cabbage (and presumably the rest of them).
I would like to know if anyone on this site has any similar experience, please?