Lockout? Deficiency?

I would do as @hashy suggested and check the ph of the run off first if ph levels are OK give them nutrients as as @easyjaygrows already said they will have used up all available nutrients. I hope you sort it out and she recovers 🙏💚🌱

Hi mate. Check your Ph if that's out it will cause lockouts. Soil should be between 6 and 6.8. Measure your feed Ph and you runoff ph. The runoff will give you an indication of what you soils Ph is.

Looks to me like a magnesium deficiency. You should feed as normal but increase the calmag dose in your solution. The issue won’t spread to new growth if you get it resolved quick. Good luck bro 💪