What can be the problem? BIO BIZZ ALL MIX, Biobizz fish mix, top max, bloom, heaven, algamic, acti vera as per schedule. No ph water, no ca mg added ever. Added guanokalong at the beginning as well.
Kinda looks like thrips and their almost looks to be one in the leaf vein of the first pic. Its small and skinny and yellow. Sometimes they are black. 5 finger leaf if counting like a clock out of 7 total leaves., 730-8pm ish. if midnight is the stem.
IPM needed. predator bugs do well with thrips. or soap and water but the life cycle will comeback.