I think he said Janice was taking quaaludes*and didn't know her lines, leaving Tom to cover for her in scenes. It would be interesting to watch those episodes to see how apparent it was.
I think because Leslie was a nervy character going through emotional upheaval(constantly) that covered the fact that she wasn't prepared.
Janice admitted that the workload and playing such a fragile character affected her own mental state. She probably took the drugs to cope with that
*Originally marketed under brand names like Sopor, they induce relaxation, sleepiness, and a reduction in anxiety
By
Paul Raven ·