Growing spinach from seed

 

I start most of my vegetables from seed in my greenhouse using a large
propagator with heating cables.I have had no trouble with starting and
growing on lettuce,leeks and onions,but have had difficulty with
germinating and growing on spinach seedlings.I use a variety which
indicates direct sowing from February,so thought that there should not
be a problem with growing in a greenhouse with some bottom heat.I have
a little other heat from a convector,but wonder if the very cold
nights have caused damping off.Is spinach particularly sensitive to
damping off?
Michael