Did you place that rack of yours out in the open under some trees or somethin ?
Just like u say BG one learns one or a few new things every year , I got a brand new idea for next year.
I plant my seedlings in a 4-5'' depression to make it easier on myself to water the plants , the idea is to dress ( in a moderate amount ) the walls of the depression with Calcium Nitrate.
You might ask yourself why and I'll tell you.Snails/slugs don't like that stuff , think they just melt away to in principle nothing if they step on it , secondly one gives the plants a nice little kick in the butt to get started on the right foot.
If I'd done that this year I would have saved all my tabacums , now I gotta be content with the different varieties of Rustica I have.
The area where I have my plot 10x10 meters has a pretty much open spaces where the grass has to be cut by the association every 2 weeks or so , that grass is just dynamite to have in waterbarrels since it contains a lot of N.