Plant is doing ikish, I flushed then finally repotted with some fresh soil around the very compact root ball which was kept untouched.
Why repot? Soil was drying too fast after all (<1day) and I didn't know anymore if I'm under or overwatering with leaves constantly drooping like hell.

Now looking at the older leafs and the veins of the leafs being quite yellow as well as red leaf stalks, do you think there could be a lack of P?

Hi I noticed your pot in trays on tent floor you need to get some pot risers to keep there roots out of run off , also if you can raise your plants up off the floor creat a air cap at least 10 cm .
warmer dryer roots aids for better plant health . Regards OD .