This will probably only work once and the pcs will get wary of it, in the goblin room past the caltrops, have the goblins only fire once, then retreat to the next room, because they can hide as a bonus action (and talk as a free one) they can have the entire next room hide then ready attacks for whoever comes around the corner. That will almost certainly guarantee a player unconscious/dead as he takes 3-5 shots as they round the corner (most with advantage). Also don't forget a 2 foot wall is either 1/2 or 3/4 cover for the goblins, depending on how devious you feel.
The fight with the goblin chief should involve someone being shoved into the pit (they get a save). And the shaman has inflict wounds, which can easily one shot level 1s.
The troll fight can also throw someone in the pit (Grapple, then just walk to the pit) It might be less damage than an attack, but it also removes that player from combat a bit.
The laboratory has a vial of toxin next to the experiment, particularly cruel DM might have a goblin try to force it down a players mouth. (something like a grapple attempt)
Similarly, you can have the players know of the rumors of the healing power of the fruit of the gulthias tree. But they came in winter, they can find the white apple on a goblin along the way. Of course if they take a bite of the white apple its 75 necrotic damage rather than healing... Maybe an OK history check reveals the fruit, but an exceptional one reveals about the white fruit.
You could also adjust the way the patrols work, basically even if they miss being attacked by a patrol during a rest, a patrol is still added to represent scouting parties returning and getting ready to return. (Just put the patrol in a logical place to restock if you don't roll enough to affect the players).
Have several of the twig blights in the last area where the players would be encountering the final encounter, rather than animating and attacking immediately, they first attack when players leave their reach with an opportunity attack (with advantage for being hidden).
Absurdly devious: If the players help the Kobolds, have the leader request them attend an elaborate ceremony granting the title of Dragonguard for the characters, all the characters are told to wear the robes and staves of the Dragonguard for the ceremony. All the kobolds in the lair attend and cheer during the ceremony, at the end they attack to attempt to subdue the characters(who are now wearing cloth armor and only have a quarterstaff as a weapon) to feed them to the dragon.
