Iron lack advice

Your Sensi Bloom feed has a descent amount of iron in it. I don't think that's a problem for you. Your idea of calmg could work, I notice the TDS is on the higher side but if they are feeding well with it no problem. an ec drop of .2 daily. a small change in EC daily is good indication they are doing well, but a larger one is a sign they need more food. I did notice some yellowing in the leaf tips in your diary photos suggesting magnesium but I don't see them in the photos you picked for this question. I was wondering if your lighting height is ok or if its to close. When the plants are getting to much light they show small yellow tips on the top growth and will not green up as fast. at 17.5" it feels a bit close but I don't know your lights manufacture. Or how to calculate the ones hanging off the sides in addition to the ones above the canopy. Last week it was at 65cm, previous week 70cm. Dropping it down to 45cm might have been to big of a change. I think your plan of giving some extra calmg wont hurt them if you keep it on the lower dose side of thing. But it may not solve the problem your looking for. Give it a shot and see how they react, maybe they will green up. Keep an eye on the EC and PPM levels and watch for some nutrient burn issues. I'd also double check your lights height as that may also be the reason for the leaves not greening up. Best Of Luck and Happy Growing!