Had to toss a whole plant, how can I prevent another?

It had brown buds all over and one bud had white webby moss and I think even tiny black seeds and caterpillars so I just tossed it. This was the first of three plants to start flowering, I don't know how the other two are doing but they look alright (except one is turning purple on the leaves and even some hairs), will the caterpillar just move on to the next plants once they near finish? Should I do anything or just wait and see how they turn out?

Also I pulled a small trinity kush that was planted in dirt this is the yield I got it seems fine I did have to removed about 4-5 caterpillars and a few buds did crumble and looked bad I've been smoking it seemingly fine but here a pic if you can tell if it's fine..

Plant one:


Plant two:

Thanks in advance for your help.

For next years grow and as a preventative measure against nasty bugs/worms eating your crop. Here's what you should do, spray BT or Spinosad for caterpillars starting at when your plants are fairly big in veg (maybe week 4). Spray every 5 days. Caterpillars come from moths that lay their eggs on your buds. The eggs hatch in 5 days. You should also spray neem oil extract every week also for things like spider mites. However, neem oil extract should only be sprayed during veg and maybe first couple weeks of flower. Discontinue neem spray after that, it will make your buds taste odd. BT spray can be used all the way up to the day before harvest without any bad taste. I've heard spinosad spray should be stopped about 1 week before harvest.

Be proactive in preventative measures to avoid those damn bugs eating all your hard work!

I feel your pain; I got spider mites once and watched a bunch of love go down the drain. Keeping bugs at bay is a never ending battle, especially outdoors. Dopechess gave some great advice.