What's Causing This Leaf Damage?

In the last couple of weeks, leaf damage has shown up suddenly on some of my Moraea plants.  It seems to start near the leaf tips and progress rapidly back down the leaf.  It came on quite quickly, after we had a stretch of several days in the low 70s F (around 21C). As you can see, there's a bit of dark marking at the center of some of the dead areas, but they do not look conspicuously fuzzy or powdery (the hairs you see in the photos are standard Moraea leaf hairs).

This has been one of the driest winters on record in my part of California, and the leaves were not particularly wet when this started.  If anything, the plants could have been a little water-stressed because of the warm spell.

The damage looks to me like it might be fungal, so I sprayed with a fungicide (chlorothalonil).  But I am spooked, so I wanted to ask if anyone had seen this before.  Do you think it's a fungus?   Could it be bacterial?  Any suggestions on treatment?

Thanks.

[Edit: The dieback stopped after I sprayed with fungicide.  I am still not sure what happened, but one theory from a fellow grower is that the pots dried out during the dry spell, weakening the leaves and allowing the fungus to take hold.  So maybe the fungus is not the cause of the damage, but an after-effect.  I'll be more attentive to watering in the future.  This is one of the problems of growing things in pots: although you get much better drainage, the it's very easy to accidentally have a drought disaster.]