Hi ballydavis. The disease that has affected Busy Lizzies over teh past few years is a fungus called Downy Mildew. I'll be posting a blog about this soon, so watch this space!
And I agree with other posts that you should be cautious not to sow too early. Conditions have been cold and dull so far this year, and seeds and seedlings need he complete opposite to grow and flourish. A heated propagator might help seeds germinate from early sowings, but unless you have lighting units over them the seedlings will grow weak and lankly in dull conditions.
It's surprising how quickly things improve during March, so get everything ready to start seed sowing in earnest later in March for those tender greenhouse crops. I can't wait!