cannot light all leds at once

Hi group: I have an arduino nano with a led in each of 8 pins (#5 to 12) Whenever I make them light individually, leds #11 & 12 do not light. But if I send a command to light them all at once they (#11 &12) DO turn on. If a command is issued to turn on #11 OR 12 they DO NOT turn on. if I send a command to turn on #11 AND 12 they DO turn on. I checked the borard, remade it, changed arduinos but no clue. Whats the catch? I am disoriented... Any Help will be greatly appreciated.

Always show us your current compete sketch.
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[code] Paste sketch here. [/code]

Show us a good schematic of your circuit.
Show us a good image of your wiring.

Typical output wiring, pick your poison:
Outputs.jpg

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Try some ginger tea for the disorientation.

Any Help will be greatly appreciated.

Yes we feel the same way. If everything was as correct as you describe then you would not see the results you are reporting. You have made some sort of mistake and so far you have not supplied enough information about what you have actually done to allow us to spot that mistake.

At a guess you have probably not wired it up like you think you have, so a schematic of what you think you have done and a clear photograph of what you have done.