DWC, 5 gal pot, 3 gal solution. Plants are drinkin...

In your photo the plant looks fine, you're not getting the yellowing to lower leaves to suggest mobile nutrients are lacking. You also aren't experiencing any leaf anomalies at the top of your plant to suggest a lockout. I think you're fine. Your EC is rising and pH lowering because the concentration rises as water is consumed and most everything else is left behind. This is pretty common while in late flower in DWC. You can lower nutrient concentration to save/extend your fertilizers but mainly keep up on replacing the water you're losing to keep your pH in range.

lockout may be causing it to not be able to uptake the required nutes

Si la CE de la solución nutritiva es menor de lo que la planta necesita, entonces los alimentos y el agua fluirán desde la planta a través de las raíces hacia el medio, elevando la CE esto se llama pro eso de ósmosis. Para la etapa de su planta debería tener un CE de 1.8 a 2. Cambie su cubeta y prepare otra solución nutritiva con un CE de 1.8

Does the EC go down or up? If its up you need 2lower EC.. Also u are changing solution every 7-10 days right. As with them drinking so much and taking in nutrients salt builds up in the roots U could just restart. Add just water. PH and after a few hours once the roots/plant have cleaned up some add nutes with fresh water. I haven't done many DWCs. But if the plants not eating. Lower ur EC until you get a drop.. Also if your RH is in the wrong window it could be causing the plants intakes issues. And been yours is 80% (just checked i reckon here's where ur issues are.