Given that setup, there are a couple of ways to share the I2C bus. You can make A1 the SCK input and connect both the RTC and LCD SCK lines to B1, and do the same with SDA, A2, and B2. You can also leave the RTC and LCD jumpers where they are and use jumpers to copy the SCK/SDA signals from A1/A2 to A3/A4.
Which version did you do when testing the connections?
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