Other mistake: Near the end of the film Bobby Campo uses a long piece of wood to set off the sprinkler and put out the fire. This small flame activates the sprinkler, which wasn't activated by the huge pile of burning sawdust and chemicals.
Other mistake: In the scene were Lori, Nick, and George are all congratulating themselves at cheating death right after George tried to kill himself. When they pour the cider into the glass, just watch the amount of cider in George's glass it constantly changes.
Answer: Janet never died before the premonition, most likely case scenario would be that since both Lori and Janet were at the theater death would be more likely to "kill to birds with one stone" which would mean that he wouldn't care about the order. Death would just want to get it done. Same scenario for Nick, Janet and Lori's deaths at the cafe, and Ashley and Ashlyn's deaths from FD3.