Most probably a power problem. I'm missing your wiring diagram so we have no clue how you're powering that setup and how the things are connected.
I cannot find any information about the power usage of the soil sensors but I guess they're drawing more than the internal regulator of the Saola can drive.
Here's the schematics.
All four devices are seen by the ESP32. it's just the wifi that wont connect if all of them are connected at first. But after the wifi is connected, I can plus all four devices and it works
A typical powering problem. Know that transmitting devices like Wifi needs significantly more power. The ESP is not a 5 volt power station. Give the Wifi a separate 5 volt power.
How is the ESP powered?
Just to make double sure I retested it and it looks fine indeed:
Scanning...
I2C device found at address 0x36 !
I2C device found at address 0x37 !
I2C device found at address 0x38 !
I2C device found at address 0x39 !
done
Thise sensors do not ducement as being capable of 4 I2C address as per the docs.
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There's also two I2C address jumpers. The default address is 0x36, but you can select between 0x36 and 0x39 inclusive by shorting AD0 (to add 1 to the address) and/or AD1 (to add 2 to the address)
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