Some Handy Help

Well hello, it's been a little while. I've been more or less appearing in picture format so here I am again textually. Today Beccy's grandparents, Mary and Roy, came for a plot visit, their advice is invaluable as I believe I have previously eluded to.
Firstly we are having problems with the Alliaceae class of crops, specifically those planted nearer to the back. The first two rows in the plot are just the bog standard Allium cepa, normal cooking onions, and they are doing great! But the Allium fistulosum and Allium ampeloprasum, the spring onions and leeks, are not doing at all well. In fact about 60-80% of the crops have failed - it isn't all success having an allotment you know. After a bit of investigation it seems that some of the manure which we treated the back section of the allotment may have contained too much alkaline. Still not sure. Perhaps the organic content of the soil might be too low and we might need to add some well rotted compost, but seeing as how we'll probably only have the plot for the next few months I don't think the compost will be fully ready, and it might be a bit late for the present crop.
The next problem is the location of the cucumber in the greenhouse. It is too far away from the door leading to a lack of ventilation and the leaves, especially the older ones, are covered in a white powdery mildew. The treatment for this is a sulphur spray, apparently. Moreover I can't control the watering of the greenhouse inhabitants as close as I'd like; I'm not there everyday. The weather has been warm and fairly humid, perfect for tomatoes, but this also compounds the mildew issue. It also causes the next issue...
...withering of young cucumber fruits. To be honest I think this is a way of the plant naturally thinning the fruits out, however it is caused by non periodic watering and dry soil in between times. I'm not too worried about this as it has about another three partially ripe fruits and about another dozen or so young fruits. I even harvested a fully ripe (maybe a bit too ripe) cuc today.
Lastly we have to mention the blight issue since I think the site has it again. Roy has bought us a particularly spiffing pump operated spray can machine into which one can pour any liquid concoction which is required to be delivered onto surfaces in a fine spray. We've fully sprayed blight sensitive crops with Dithane using the afore mentioned gadget. Those crops include the tomatoes, which on an interesting note, are fairly closely related to potatoes. So far the crops are blight free touch wood and we're taking full precautions.