Is this definitely CalMag deficiency? Check diary for video.

Please before doing anything, give enough water so you have runoff. Check the first little bit of that runoff water to see what your ph and ec are at. Ph is normally the culprit and if the ph is ok then see if your ec is low or high. If it's in a good range, then and only then give her what you think she needs. Going overboard on cal/mg if it isnt really needed only creates more problems. Cheers friend

Also, while I haven't used those nutes before, it looks like you're feeding really heavy. Your ppms should be between 700-900 now. Get a cheapo EC meter if you don't have one. You can get one for less than $10USD.

In regards to what amount, if you have a ppm meter I rock 150ppm of calmag. The bottle will also have directions on it as well. Cheers,

Heya MrGreen92, Indeed it is. I would use a little calmag next watering unless you know your pH is off. If your pH is off the plant won’t be able to uptake nutrients at certain levels. I see you’re using soil, for soil we want to maintain a pH of 6-7. This was the first deficiency I ran into when I used basic soil mixes. Cheers and good luck!

And also how much CalMag do you recommend to correct this? Thank you for your help!

To me : Yes !