This is most likely a cal/mag issue - but the question is why! You don't give any nutrient information in your diary so it's hard to figure out what you should be doing/not doing. Cal/mag issues normally result from improper PH in the soil... have you been checking this? Have you checked the PH of your runoff? If it is out of whack (the range should be between 6.2 and 6.5 for soil - outside of this range, calcium is not going to be absorbed), you'll need to do a flush (since they're in about a 1 gallon pot, run 3 gallons of ph'd water through her), let her dry out completely and then resume your normal feed making sure you PH it to 6.2-6.5. That should put you on the road to recovery... do not expect the leaves that are damaged now to improve... you'll only see your success with the new leaves.
Good luck!