I believe this is a deficiency. I had a plant with the exact same issue, and I could never quite tell if it was just purping up, or a deficiency. But I lean toward deficiency because if that marooning of the margins spreads to the flowers, it can cause bud rot. I witnessed this first hand. Putting her on a CalMag regimen, and heavy N in early flowering seemed to help, but I couldn't tell you what the deficiency is exactly.
This is a seed found in some don shula from an IL dispo no idea what the other half Is for sure but based on how it's has grown and looks so far I'd say it is pure don shula and got pollinated from a herm it very much took after the white and is absolutely caked in frost. I don't believe the power outage caused it but I did think to mention it. I'm honestly thinking I have to much phosphorus because I did 2 feedings in a row instead of every other because it was getting a little too light in color.
How hard cos that could be causing nute lockout specifically phosphorus if you overfeed too much N that can do it same as if temps stay below 15 c for too long that can lock stuff out too
I normally do half strength by the feeding schedule for the fox farm line and feed every other water but I fed 2 in a row because it was looking pretty hungry and my temp is very consistent with my ac infinity system it's stayed at almost a perfect 74 rn plan to lower a little closer to harvest
