anyway you could just move the one under the hps to give it that extra light? i had a problem with one awhile back....i topped it above the second node and only had 3 shoots appear but moved it under more light and eventually it caught it. It was kinda shaded by another one of my girls so idk if this will help or not.
lol so its funny to come back and look at this pic. nothing ended up growing besides that one branch so i clipped the main stalk right above the new branch and now that one branch has grown to a full sized plant and is keeping up with the others.