Brown spots on some leaves

High bro, Your EC went up because you plants are drinking more water than nutes. Lower your EC and adjust until they keep the same reading. When you give the right amount the value will stay stable. The beauty of a DWC system is that you can refresh your water and nutritions really easy! I would refresh the whole system with pH 5.7 and EC low (for the stage that your plants are I would say around EC 1.5). Then continue growing like you did before. They look beautiful! Happy Growing! 😋

somewhere I read that an excess of an element can be similar to a deficiency .. type cal mag K

I see a small excess of nutrients ... a few days with less ppm .. max 700

This is actually a deficiency caused by the too high temperature of the nutrient solution. Get yourself a water cooler for aquariums or make sure your pumps distribute cold air. The increased temperature also promotes the growth of unwanted fungi and bacteria, so it's better to act sooner rather than later. Good luck!

I get bits like that u wouldn't worry plants looking good happy growing

Do you change your water once a week since it has been budding? Also, check your roots and make sure they are still fine and dandy. After that, test your pH and nutrient levels, as well as checking your media, which may need flushed. One of those things is probably the culprit. Or, depending on how far along your buds are, it could just be fade. I hope this helped. Good luck!