Daylight (in photography) is not an absolute color, it's more a vague wishful dream. Liberties are taken. :)
The various light bulbs will simply vary greatly, each brand and type. Your gray cards will vary slightly too, and 18% gray cards are really too dark. Gray WB cards are much lighter, and I'd suggest a "white" white balance card, the Porta Brace is only $5 at B&H.
Your work is OK if you have the reference to correct it. You click on the neutral card, telling computer "This spot is neutral, make it be neutral", and it does, and removes the color cast there (result has equal RGB components, no color cast).
Here is a sample of several cards, with the same one flash illumination.
It is JPG now, and it's been corrected once, but you can still click around on it.
Clicking in Raw, on 4 gray card brands at top, from top left to right, I get
6300K -13 tint
6400K -3
6300K -4
6450K -4
The two small gray cards down at left
6600K -3
6750 -3
The WhiBal card in center 6350K -6
The large white foam board everything is mounted on 5750K -4
Across the bottom, left to right:
The two white Porta Brace WB cards at bottom
6400K -5
6350K -8
The sheet of plain white copy paper 6500K -11
The cheap white envelope 6300K -9
Clicking around on the same card often gives slightly different results. Not so much that it actually matters. About any try is greatly better than no try at all.
Flashes all vary too. They claim Daylight, and they're usually halfway close, but they could be a little low, or 1000K high, and also with a color tint. Flash color WILL vary with their power level. They also age and shift. Light bulbs too. Excepting perhaps bright direct sun, we always need to correct white balance. The flashes and light bulbs will vary more than the gray cards do.
But any situation can be made pretty good if you have a reasonable reference to correct it.
