Prior to starting my first NG+ run, I was at 295 Toxicity capacity, just enough for four decoctions and a 15-point potion such as Cat. After starting NG+, I dropped down to 292. I got that back to 293 by starting the Mysterious Tracks contract and getting far enough to learn the Chort Lure recipe so there must be at least two other quest recipes that I need to re-learn.

I figure the drowner pheromones recipe is another I can pick up, though I already have the actual drowner pheromones potion.

What other quest recipes do I need to re-learn to get my Toxicity capacity back up to full?

If your maximum toxicity is that high, then presumably you have Acquired Tolerance. In NG+, you retain all of your learned alchemical formulae except for quest recipes, I believe. So you are likely missing recipes for one or all of drowner pheromones, Pop's mold antidote, shaelmaar bait, and/or the mutagens used in the Trial of the Grasses. If that is the case, you will learn these anew as you progress through the appropriate quests.

That is just what I was looking for. Thanks very much.

Well, I did the Muire D'yaeblen contract, the one with the drowner pheromones, and did NOT get an extra point of toxicity capacity; I'm still at 293. I haven't pushed the story line far enough to get Pop's mold antidote so I haven't been able to test that one yet but I'm going to try to get it within the next few days.