That's awesome that you got some water-soluble fertilizer! And the secchi disk will be a big help.
I would wait on the Cutrine. And it may not have been your application of it; I've known more than one pond owner who used it and got anything but a great result with the FA
Ideally you'll get a bloom within a week or less; if it's going to happen with this application you will probably have it within two or three days. If the bloom doesn't materialize with this application, the 12th would be a good time for the next one, but the 15th or the 10th could also work. The 10th is enough time to know whether or not this application is going to work or it's going to require another one in a short time period.
Probably the bass bit the dust because that's the area where the most Cutrine was applied; most likely you did manage to kill some of it, and he just didn't have enough sense to swim to a part of the pond with better DO. It sucks to lose a nice-sized bass, to be sure. But you'll have more.
If you get a bloom from this application, you definitely would not need to, or want to, fertilize again in two weeks unless the bloom is already significantly dissipating by then. Normally the second application comes two weeks after the first because the first one is done in early spring and there will have been at least one cold snap that knocks down any bloom, within two weeks of that first app; that doesn't apply here, so the only reason to do it again in two weeks would be if this one doesn't take.
