Say what?Well I can tell you straight away what the issue is.
You have PLANTS, that are about 30 - 45 cm tall, they might be cuttings but they need Cal Mag . Period, that IS 100% no doubt where you are going wrong... your plants are cuttings with roots, I would say that they should ATLEAST be classed as week 2-3 in coco, im familiar with Hydro but COCO is similar, drain to waste should be higher in ppm than hydro you say you are feeding them ONLY RO water and Molasses.
Wrong combination any experienced grower would tell you that ALWAYS... MUST... ADD CALCIUM AND MAGNESIUM SUPPLEMENTS TO R.O WATER. The only exception to this is to feed seedlings and for ROOTING a newly planted cutting, im talking 3-5 days MAXIMUM without Cal Mag
Any plant that is of that size is 100% going to be starving for nutrients, specifically Cal Mag. You would only also consider not using Cal Mag if you were using Tap water. As Tap water has anywhere from 80 - 180 PPM calcium and magnesium, and very little Micro nutrients.
I know you are probably scouring the internet for photos of Cal mag deficiency and you are thinking that it isn't that malnuritionment because your leaves are displaying the TYPICAL CALCIUM deficient medium, your plant NEEDS calcium and magnesium in combination together always in your water to be able to unlock its ability to TAKE UP the other fundamental nutrients like Iron or Zinc etc because they are locked out, they do not have the cal mag they need to transport energies and other nutrients from its roots too its canopy. So you are therefore experiencing a general nutrient deficiency. If you want to correct this, you must always mix CalMag into Plain RO water first, followed by other nutrients even if they seem smaller and in adequate, it is essential. pH balance is done last.
I would also definitely be using full strength week 2 veg nutes ppm guide, and increase by 30 - 50 ppm a day until u see burning, then drop it back by 50 ppm and use that as your guide to what you know your plants need. Underfeeding is alot harder to correct than over feeding is because overfeeding burns all tips the same, deficiency causes big problems in large fan leaves that are needed for development.
So use cal mag, and start feeding plants from week 2 guides with micro and macro, ide say 160-360 ppm depending on your nutrients as im not as familiar with.
Ya make that your base now. When you add nutes if your tdg goes high, water it down with ph’d water. Works for me. My solution goes up really high week 6+. I have to water it down to prevent lockout. I do use SLF-100 which is how I haven’t had a water day or a flush this whole run. I’m really impressed