Well I don't see any dead spots so that is not magnesium problem. If it was Magnesium then the end of the leaves turn brown and curl upward.

It's hard to tell the pictures are not the greatest of quality.

Are the stems reddish or have red streaks?

It's unlikely it Iron immobile you only really have that problem with high Ph levels above 6.5 and you grow hydro so that should not be a problem for you.

Are the leaf stems purple? That would be sulfur immobile problem but again that is tied more to high Ph but anything is possible.

From what I can see I would take a guess of Nitrogen mobile problem. Try adding some fish shit, bat shit, or blood meal to your nutrients they are almost pure (N)