Please help identify and fix deficiency!

could be nute burn for the yellow tip leaves (or too close to light) and the patchy brown spots could be calmag def?

Propably roots starts rot or lights are too close. There is no chance of deficiency in the dwc, there may only be problems with their absorption. If u have any problems always make new solution. Remember to shake the bottles well. First add calmag / micro to the water and mix the water well after each fertilizer. Make sure to add some microorganisms (orca, bm) to your water. If u use led lights and your grow room is cold (below 25c) add cal-mag in small amount (1ml per galon or something like that). Invest in a good air pump - they make the difference. Keep space near the plants clean. If u use ro water, add 10-20% tap water (at least with ghe nutrients xD)

Man this can be unfortunate. Looks like you're not having enough drainage.. Allow plants to dry out and then gradually increase water as plants recover. https://www.growweedeasy.com/cannabis-plant-problems/root-problems-cannabis