Is this Calcium Defic? What to do to fix?

rusty spots are more likely Mg defeciency, i think. Either way, CalMag has both, but if you already provide a ton of Ca, you may exacerbate the problem or it could actually be a lockout from abundance of Ca from the start. If you find that's the case, epsom salt (magnesium sulfate) is another option for Mg deficiency. pH should be fine at 6.2. You could try a slight increase to your pH before doing anything else. Both Ca and Mg are more avaiable for use at a higher pH. Try 6.5. Now, i'd also consult labels / brand website of your main nutrient product. If they suggest a pH, i'd stick near there, reassess and choose a different path to try to fix this particular problem. What they suggest is likely best for the specific chemical makeup of that product. Using above and beyond their base A/B system or whatever muddies that up a bit, but likely still the best starting point. So, the answer depends upon what you've done recently and how the soil was fortifed (e.g. any garden lime, gypsum etc..) - and a lot of that is impossible to know in a precise way in many situations. Check the guaranteed analysis of the nutrients you use... even find a nute calculator online and tabulate PPM (think the one i link in my main GD profile comment area is working for liquid nutes, if an online calculator isn't accounting for specific gravity, it is not an accurate conversion). Ensure you are not bombing it with Ca or possibly P or K or common culprits too due to common 'bloom' products. Eliminate possibilitie as best you can and make an informed choice. You've already begun one potential solution. Might as well observe for a week or so unless something crazy bad happens - if it does, Ca-tox is a real possiblity for this context. I'd still do the math on the PPMs of what you add from your fertilizer mix, since that has no impact on the plant, and might reinforce your hunch or point the needle somewhere else. That type of knowledge, even if just a ballpark, can help greatly when trying to deduce what is going wrong with the plant.