Anyone Have any Idea what the discoloration on the...

Hello @OnUrSixx ! That is a little calcium deficiency. Nothing to worry about as long as you don't see an aggressive progression of the problem. Have in mind that your water needs to have a value of EC at around 0.3-0.4 ms/cm before you add any nutrients. If its lower then add some cal/mag until you reach that value and then add all the other nutrients. Happy growing ! :facepunch:

Hi @OnUrSixx! I think it's either pH fluctuations, or a slight nutrient deficiency in the past weeks (Manganese, Calcium, or Phosphorous...hard to say with the informations & pics you provided). I won't worry too much at this stage, since the plant is looking healthy and is now under a good feeding routine. Keep an eye onto this leaf (and the others), try to stick to the correct pH range, make sure your pH-pen's calibration is fine, and I'm confident you'll be rewarded with a great yield. Happy growing :facepunch:

Hi, I think your PH was instable.That the plant can get all Nutrients, the Ph got on hydrponics on a Range from 5.5-6,5. Otherwise the plant misses those nutrients and show those marks The plant will recover, but the Marks will stay. In addition i let you a link for best Ph range https://www.growweedeasy.com/general-hydroponics-nutrients

yeah anytime the plants feel a lock out of nutrients or a calcium deficiency when they're growing, it kinda leaves a mark on the leaf and this follows the plant as it grows like a scar, never fully recovering. Battle scars OUSixx !