When two or more of these modules have their 5v pins hooked up to a common 5v rail (power off) and I connect an 4-pin SWD st-link to the programming pins of one, I'm finding that all modules (and peripherals attached to them) power up. In other words, the 3v3 from the st-link is powering everything. The voltage on the rail is 2v6. Would it be better to have a diode between the 5v pin of each module and the 5v rail? Thanks for your thoughts.
This shows both the mcu board and the swd st-link board: