DND 5E – How to Find Herbs for Potion Crafting

Telegraph your decisions excessively, and allow retcons

In my experience, what the DM is thinking is very different from what the player is experiencing. In the example you gave, while you "already knew the weight limit," the player did not. From his perspective, then, you randomly collapsed the platform.

I deal with this issue by not only telling the players what the characters see, but also what the characters judge. For example, instead of telling your player "you see a crumbling platform," you can tell your player "you think the platform might collapse at any moment". In "real life," the characters have a wide range of experiences and perceptions that you can't possibly convey in a reasonable time as a DM, so telling the players what their characters think is an easy shorthand--the players are always free to disagree or probe more deeply, if they choose.

It's always going to be a judgment call on whether you should call for some knowledge-based roll or how much information to give, but I would err on the side of giving more information, to avoid instances like the example above.

Additionally, I let my characters do minor retcons. When your player decides to go on the ledge anyway, you can say something like "the ledge feels like it's about to give way under your feet". If the player changes their mind about going on the ledge, I let them do it.

It's going to be annoying, and it will feel like you're giving everything away, but it ultimately leaves your players feeling like they have a much better understanding of the situation and the logic you're using. Moreover, there might be some situations where the players will want to go on the crumbling platform--in those cases, they will have a good idea of what they're getting into.

"Gotcha" moments suck: focus more on avoiding them and less on mechanical surprises

Here's the thing: even though you're literally pitting the players against adversaries, the DM-player relationship in 5e should not be adversarial. I put in terrain and traps so that my players can have fun defeating them, not so that I can spring surprises on them and laugh evilly.

Even for actual, hidden traps, gotcha surprises are terrible. From the player's perspective, they get put into difficult, damaging situations totally out of the blue. Indeed, when I play traps, I give the players a few seconds to try to respond to a trap activation, just so they have a bit of agency ("you hear a click when you open the door, what do you do?"). By boosting player agency and letting them understand what you're thinking, you can reduce the number of gotchas and likely reduce your perceived unfairness.

Reset your player's expectations

Now, in order to implement this new DMing style, you have to fix your relationship with your players. After all, this problem is not only coming from you, but from your players as well.

You should talk to your players, tell them that you're going to change how you're DMing, and see if they're willing to reduce their combativeness. Hopefully, this "reset" will help your future sessions go more smoothly. Again, you can see this as part of making your intentions more transparent and more explicit, and hopefully your players will appreciate that.  

I play a druid character who regularly uses conjuration spells. To make life easy on my DM I prepared a cheat sheet of all the summonable subjects. It's just a little sheet that has AC, relevant abilities and a hit point marker for each summoned creature. If there are 8 creatures summoned for that CR, then there are 8 hit point markers. He usually has me run them for him, but he still makes the decision. Each entry on the sheet has key words that can help him make a quick judgement call: underground, flying, darkvision, poison, etc.

When I cast the spell, I tell him what my character is hoping will appear, usually using a keyword. If I am hoping for air support, I might get owls, or bats. For poison, I might get snakes or spiders. Part of the fun of D&D is dealing with surprise results (one of the main reasons the game has dice).

So yeah, if your players intend on making a lot of use of these spells, some prep work ahead of time can be helpful. If you can convince them to do the heavy lifting (as I did for my DM) so much the better.

In general, the DM should make something appear that has some relevancy and helpfulness for the current situation. The player is expending a spell resource, after all.