Cabbage Seeds - Problem!!

Good Morning All, I have started sowing cabbage seeds this year for the first time, planting every 2 weeks so far.  They are in an unheated room, temp between 52-58 degrees.  They are near a south facing window, with silver foil behind to prevent "leaning".  The issue is this: so far the first 2 sowings (5 and 19 Feb) have taken and are growing well for "Offenham 2","Langedijk4" and "Greyhound".  However the "Golden Acre Primo 2" are starting to become withered and papery round the edges of some of the leaves!  All sowings are in 6cm coir pots.  Any thoughts, (too much/not enough water) or maybe just a bad batch of seeds (Mr Fothergills).  Many thanks.