Novice grower experiencing problems, possible deficiency.

[Faddenator]

Thanks for the replies guys! Appreciate it!

Is it too late to undo/repair the damage done would you say?

Will this mistake have a dramatic effect on yield/plant height in the future?

No, it shouldn't have any significant effect on yield or height. the only problem you may have is slow growth for the next few days, but once you correct your watering they will start to shoot up.