Zunami 5 weeks old losing colour

She looks pretty happy to me, if possible though increase nitrogen and reduce PK for a while

K excess and lockouts

Looks like she’s hungry That pale green usually means nitrogen deficiency or roots not taking up nutrients properly. Since you’re in coco, make sure you’re watering often (every day or every other day) with proper runoff and pH around 5.8–6.0. Don’t switch to soil yet, just fix the feed and she’ll bounce back

Just give water for next 2 feeds let here dry out on top, you don't need to water till run off when you think you have this problem break the cycle of what your doing and water less until roots recover if that's you theory.. Good luck

If your not into the coco and really want soil stick a seed in soil but I wouldn't bin this plant the lighter new growth is normal waiting on chlorophyll to fill leaves and turn darker, I would be patient she looks like a really nice plant, remember with coco you need to add everything they need because coco in an inert medium and same as growing hydropics, Calmag is needed more than soil, npk, macros it all needs to be there, normally a coco feed will do the trick to the most point.. Canna have a good 1 it's only 2 bottles all the way threw I also add Calmag and then pk1314 in flower, it's a learning curve but once pinned down it's a game changer.. Good luck..