CalMag or Lightburn?

Is it only present on the sugar leaves or is it present on other leaves too?

This is burning from feeding too much.....or too often...........or both. It is not a cal/mag issue. At this stage of the cycle, it can often be attributed to never watering properly with adequate run-off each time, leading to a build up of nutrient salts in the substrate, causing the burning. Only you will know if the lack of run-off is a contributing factor. Remember too, what is showing today in the leaves is a direct reflection of what was occurring in the root zone 2-3 weeks ago. I suggest you give just plain water in normal amounts for the next 7-10 days and when you resume feeding, half to three quarters of what you were giving previously should be enough.

looks a bit overfed (very dark/lush), but could be the picture playing tricks, too. light burn could start that way with some interveinal damage, but if this is "normal" as you say, you should be changing hanging distance or light dimmer to stop this from re-occurring. That only is a negative if it is 'usual'. easy to eliminate this as a possibility.. is it occuring underneath in more shielded/shaded areas? if so, then it is not light-related i see a pistil changing rusty color, but not the cola itself. at least in the 1 pic provided.

It's very likely to be Calmag, especially considering you're in the flowering stage. You should check the EC and pH values in some runoff to see how the growing medium is doing and understand if it's a deficiency or a Calmag blockage. If the pH is low and the EC is very high, you have a blockage; otherwise, if you have the correct pH and the EC is lower than the input, it's due to deficiency.