Don’t give it calmag anymore that’s why it looks crusty and leaves are bending and burning.
You have been giving it to much nitrogen as well, that’s why your leaves are almost black! The nitrogen makes the leaves green.
It needs phosphorus and potassium in flower not so much nitrogen anymore.
You should have like 20-22 degrees at this stage!
And maybe 18-20 at night.
Your rh should be 40-50%.
Good luck with your grow 🙌🏼🔥