So what's the deal with this plant? Is it growing in coco? If so, you are not feeding correctly. That's definitely signs of a calcium issue. PLEASE remember, that a deficiency sign DOES NOT automatically mean to "add more". Plants that young don't need much of anything. If a calcium issue is showing this early, then its probably a lock out due to excess nutrients or ph being out of range.. Meaning that the calcium in the medium has been locked out and is not available to the plant. I have never and will never, recommend calmag for that reason. They are two completely different nutrients that have totally different deficiencies. Not only that, excess calcium will lock out magnesium... Excess magnesium will lock out calcium. Excess calcium and magnesium will lock out potassium. And so on...
If you are growing in coco, you should be doing light feeds/waterings every day. Coco should be treated like hydro. If you let it dry out, the ph levels get way out of range.. Which also locks out nutrients.. Which could also be at play here.
Think of it this way.. You know you are feeding the plant nutrients.. Even giving it Cal mag.. So if you start seeing a nitrogen problem for example, when you know dang well you've fed the plant NPK.. Then you should start thinking along the lines of lock out. Caused by ph of the medium or by excess of certain nutrients. With the plant being as young as it is, it could be either one, or both at play.