What could be wrong if mix has egg shells and water is phed at 6.5 before watering, but still Ca issues?

Normally, any nutrients you give your plant already contain sufficient calcium for the plants... calcium deficiencies arise because of either a pH being out of range for good absorption (it needs to be between 6.0 and 6.5 so yours is good - a little high but still good) ... OR it can be because you've been giving them too much nitrogen which will cause a lockout and the plant won't be able to get to the calcium that's already there. If there's a lockout, it won't matter if you give the plant a whole bottle of calmag (and eggshells will only give it a small amount of calcium)... the plant won't be able to get at it. Since you don't have a diary for this grow, there's no way we can tell if you've been overloading with nitrogen so you're going to have to take a look at that yourself and try to figure it out. If you have, you should flush you plant with 3x the pot volume with pH'd water to rid the soil of the excess nutes... let her dry out and when you resume feeding her, the first feed should be only 1/2 strength but cutting back on any nitrogen-rich nutes even further. Going forward, you should only supply at MOST 1/2 strength of the nitrogen-rich nutes and increase your bloom nutes. Good luck! Do start a diary!