And definitely a deficiency as Hyroot and I both initially suspected. The flush I recommended, as tenthirty explained is to essentially start from a clean slate. You then know what's there because of what you added. Plants do not assimilate nutrients all at the the same levels and so overtime you can get salt buildups that will re-suspend in solution upon watering and throw concentrations off causing other nutrient problems even if pH is good. Looking at the pictures it appears you need to bump up your feeding all around. I'd increase buy 25%. So if you use 8ml/gal 25% increase would put you at 10ml/gal, 8*1.25=10 or (8*.25)+8=10. See how that does. If a little burn, back it off to ~12% so again if using 8ml/gal go to 9ml, (8*.12)+8=8.96. If 25% seems fine and they still have that pale appearance go up a little more and find what they like. Some plants are heavy feeders while others are not, just as some are more finicky than others.