Looks like magnesium deficiency to me.
Maybe link the diary to the question so other know where to look for it.
growdiaries.com/diaries/159766-grow-journal-by-sators
it spears to be this one. but you have not given them any nutrients in the last 5 weeks and sparkling water. I feel this is your main issue. Even super soils need to be amended once in a while. Magnesium flows out of soils easily so if your flushing them every week for 5 weeks it most likely has none left. you also do not want to flush soil, you give water but not in excess, this is my personal experience from it all.
Good Luck!