Some form of deficiency..... please help.

Hi there please see pics...... 3 x devils harvest shorline. 2 out of the 3 plants are struggling and appear stumped in comparison to plant 3. They also seem pale and yellowish. Any ideas on how to correct as they were meant to be ready to flip by now.
Canna coco
Canna nutes

how often do you feed at what ppm? looks like they need more food to me.

Well it looks like a nitrogen issue, a bit low I would say, that is the issue with 2 part nutrient lines. I say this because it has yellowing along the tips following inward along the leaf vain. I would pick up a nitrogen booster and follow the instructions on the package. I would also hold back on flipping due to this problem. With deficiencies they only grow larger and cause more problems lowering they yield, quality and waste time.

Feed every 2 days using canna schedule reduced slightly comes out at 700ppm and 5.8 - 6.0 ph. I thought nitrogen def so purchased canna mono nitrogen and added to nute solution approx 100ppm, its been a week and no sign of improvement. Its hard to believe all 3 plants came from same packet, were all planted together and are fed / treated the same.