Verbs and Grammar

I imagine one should never try to learn a language by studying grammar first. But eventually, one has to study grammar. I have postponed really really studying verb forms but I have had to feel my way into them as it were gradually. Is there anyone out there who will answer a simple question?

The third person plural feminine of the imperfect - tiqtolnah - appears to be identical with the second person plural. Why isn't the third person plural yiqtolnah? (like the 3pp masculine)

The paradigm looked like a misprint to me - but it was the same in my Lambdin. After 15 months of slogging, you would think I would not have such a dumb question - but there you are. I do.