Dwc yellow centre

it needs nutes. its a dwc. it should be ever-present. The concentrations of 1.3-1.5EC (ignoring what your tap adds, may need slightly more with co2 supplementation, maybe?) is safe even for young plants, but you can dilute it a bit that first week or two if concerned. First hint of paling and you should give it the right amount going forward. keep the pH around 6. if shoowing for 5.5-5.8 don't err on low side or you'll lockout Ca or need to add excess amounts of it which will then domino into another problem, lol. things should run smoothly when it comes to nutes - within a grow or 2 at worst you should have it figured out in soilless/hydro context due to the fact you know exactly what you are putting into the rez compared to all the unknowns of soil. it's one of the easier things you have to master for soilless/hydro context, if willing to self-criticize in an effective manner. basically, when things go wroung, it's your fault and not some ghost or "i did everything the same with each plant" -- clearly doesn't matter to reality, lol. reality don't give a shit about lame excuses. avoid the gimmicks and overpriced fertilizer. I spend 30-35/year for roughly 80sq ft of plants per year. It's less than 2.50 usd per pot for fertilzier. 4 cents per gallon mixed and i waste a lot of water since i switched from hand-watering. No nonsense supplements needed to make frost-caked buds.