No you are defintly not screwed. Your plants look fine, hence you still have time to correct the issue.
Get a good Calmag supplement, preferably low in N, so it wont change your nutrients ratio too much. Maybe run one fertigation with only Calmag added to the water (and pH corrector if nessercary). Just add as much Calmag as possible to get your current target EC.
From there on, just add the Calmag to your regular feeding mix, at least at 50% of the recommended dose. You might have to reduce the amount of other nutrients to maintain acceptable EC.
Good luck!