I'm not so good with pictures but I will name two. One has happened multiple times and I think I'm not the only one on this: many times I decided to try an experiment. Either two or more varieties side by side to see which I liked better, or the same variety with different treatments to see which works best. Do I need to label them somehow? Nah, I'll remember which is which. NO I WON'T and neither will you. Either put indelible labels on the ground, or record the difference on a map.
Others' story reminded me of my squash bug problem, particularly my first year here. It got kinda bad by the end of the year, but I still had decent harvests. I left the mulch in place, figuring cold would kill the bugs. The following spring the squash bugs completely killed my winter squash, summer squash and melons. The next year I waited till July first to plant squash in that garden and never saw a bug. Maybe the little cucumber beetles, which don't do significant damage but one year they brought in mosaic disease that ruined my zucchini. I don't use foil and get good squash nearly every year--I just spend a little time, as much as every other day, investigating each leaf of my plants and removing egg patches. I squash any nymphs or adults I find. And throw the leaf bits with eggs into the wood stove. If you grow a great deal of squash this isn't practical of course.
I have some advice on carrots. I don't know why they wouldn't germinate, except that they take a long time, aren't planted deep and require moist soil, so you may have to water every day for a couple weeks. But I have found two tricks that really helped me with carrots--I'm still eating last year's carrots, which spent the winter in my root cellar. First, I have clay soil so I plant Danvers or Red Cored Chantenay, and I add sand as well as compost where carrots will go, and work the bed finely. The other thing--I read somewhere that planting alternating rows of onions and carrots, the carrots repel the onion fly and the onions repel the carrot fly. True? I dunno but I've been getting much bigger carrots AND onions so I keep doing it. I plant onion sets in rows a foot apart across my bed in March, and then in April, when the onions are up and easily visible, I plant a row of carrots down the middle of each gap, for rows six inches apart. (Also I finally realized that onions need a lot of water, and that thinning the carrots earlier would make for more big ones).