Strain
I'll give them a high rating because it was probably the conditions here that were the problem. However, all being treated equally? These really didn't hold up very well compared to the ones around them. Not a good strain for very (very) hot environments and probably more suited to a controlled grow tent setup. Of course, that costs electricity and makes it all rather expensive so that's no good to me here :)
In fairness to Sweet Seeds - the F1/Fast Version plants I've got on the grow are doing really well.
But they've gone from 100% reliable to not-so-good in the space of about two years. Three years ago when I started (and I haven't changed much these last few years) they were the go-to breeder for me and they were much better than the competition, but now they're not the same as they used to be.
The general yield, except for one, was pretty damned low.