what's this? (FLOWERING)

You are right, this does not look like normal shedding.

This looks like nute burn. Try reducing the nutes to 1/2 concentration and see if the leaves continue to suffer. Your plant is a tad small, so she may not be able to metabolize all the nutes you're giving her. I would presume, by the look of things that it has too much Phosphorus.

Oh... soil with slow nute release... and I was here scratchin my brains what could be wrong.

Never use time release soil ever again. You will always have a disadvantage when dealing with this kind of soil. It will nute burn your plant or cause deficits, because you can never control how much nutes your plant is getting. Plus, even if you flush at the end, your buds may still retain some nute aroma.

The best thing for you to do is change the soil. Seriously. If you want to get rid of the problem, that's all you can do. If you don't want to transplant, try not giving your plant any nutes for 1-2 weeks. This can have 3 outcomes:

1. Your plant will still get nute burned. => You definetly need to change the soil.
2. Your plant is just fine. => The amount of ntues released by the soil are perfect for your plant right now. There's no need to add any nutes.
3. Your plant will show deficintes. => The nutes in the soil are not enough and you will have to start adding nutes to the water. This outcome is the most improbable.

I say wait a bit, stop giving nutes and see which of the 3 possible outcomes will come true. Then you'll know if transplanting is absolutely necessary.

Transplanting is still better then nute burn.