It's been a big week for my lady! She got more space for the roots :D
The lower fan leaves were getting yellow faster than I would have liked them so that meant transplant time has come! I was also suspecting salt build-up at the roots, but the last run-off I checked was on 1.5 EC which is the same as what I was feeding her.
Anyways, I flushed her just in case(as suggested by Mrs_Larimar) with 30l tap water, and gave her a 10l feed right after transplant.
There was no mark about the size of the pot, but I finished a 50l All-mix soil bag on her, so... I would say she's in a 45l pot right now.