k - deficiency?
you've been irrigating with ph'd only water for 10 days? i'd lean toward a deficiency, but if it was recovering you'd have to consider that too... how's it changed lately?
could be Mg-deficiency too -- those take 4-6 weeks to show up. consider a longer period of time to eliminate this one or confirm it etc...
low on leaves means it is a mobil nutrient.
other things can give a false positive for nutrient issues -- but under your context, i doubt buildup is possible with 10 days of irrigation. You've controlled your pH, too... so, feel confident about feeding again...
if you check my answers, 9/10 i tell people to back off. i try to be extra conservative when recommending ramping up or resuming after any toxicity.
Anyway, i'd say it's safe to fertilize again, and likely needs it. if you were water-only for a reason, consider adjusting your feeding formula a bit. what was the original cause for the flush? adjust that component a bit.