Was hat sie?

Hello my friend. No panic, but now it's time to be vigilant. Your pH levels (6.3) and EC levels (1.9) are quite stable for a flowering phase, but those "rust spots" on your blueberry are classic signals. ​1. Likely diagnosis: Calcium (Ca) deficiency. ​Symptoms: These small brown/bronze spots that appear in the middle of the upper or middle leaves are typical of a calcium deficiency. ​The connection with pH: Even though 6.3 in soil is a good value, calcium can sometimes be less well absorbed when the pH fluctuates or the EC is slightly too high, leading to competition with other nutrients. Blueberry: This is a strain that can be somewhat sensitive to the need for micronutrients. ​2. The EC at 1.9: Beware of accumulations ​An EC of 1.9 is quite high (depending on your substrate). If you are in soil, it can start to saturate the environment. ​Blocking effect (Exclusion): Excess potassium (K) or magnesium (Mg) can block calcium uptake and lead to these rust spots, even if calcium is present in your fertilizer. ​3. Is it serious? ​Short-term: No, if it remains limited to a few leaves. ​Long-term: Calcium is essential for building the cell walls of the buds. If the deficiency progresses, it can lead to a slowdown in flower development. ​My recommendations: ​Cal-Mag: If you aren't using it yet, add extra Cal-Mag during your next watering. ​Light flushing: You can water with clear water (adjusted pH) to slightly lower the EC of your substrate and "reset" the root area a bit before continuing with fertilization. ​Monitoring: For now, do not remove any more leaves. Use the affected leaves as "witnesses": If the spots do not grow and do not appear on the new leaves, the problem is resolved. ​In summary: It is likely a small calcium hunger or a slight blockage due to a slightly high EC level. Adjust it carefully and everything should be fine. I hope I could help you. Have a nice day and a good grow.