Looking rough.. ride it out because you are so close... if canopy completely dies off, pay attnetion to how the plant is drinking.. if it just stops or nearly stops, it'slikely dead, lol.
I would keep going as long as you see development and you don't see it rot on the branch. smell will be a big key to use as an indicator too.
The plant won't last long if there isn't enough green. As long as some exists, it's got energy to develop still. how many days beyond ? no idea, lol.
check smell, chekc for rot... check for development, and take it day by day... looks like you have some time left.
If runoff is 5.6, it could be even more acidic than that. Ease off on nutes.. east off on cal-mag, if you've been giving it, it clearly isnt the solution.
ca and mg deficiencies can be caused by P/K toxicities too.. as well as pH issues... adding a bunch of cal-mag could have potentially made it worse. always be certain before you add things.. always better wait and see. ensure to eliminate other possibilities before doing anything that involves putting stuff into your susbstrate or reservoir.