I want to thank everyone who responded with advice for my last post.
Per the advice I received, I went ahead and found a 10-10-10 Scott’s fertilizer. I tried to apply it or the instructions, mixing it into the soil, and watered it in. I’m hoping for good things. One thing I’m curious about: the instructions indicate this particular product should be applied every two months, which seems like a long interval. Shouldn’t I be fertilizing more often? Did I choose the wrong kind?
Also, I finally got some straw and used it as mulch. It seems like it’s keeping the soil wetter for longer.
As for my plants: 
My potted tomato plant is taking off, more so than the ones I have in the actual bed. I installed a stake and a cage. I had primed of the first flower, but I believe it may be ready to bloom again. Do I need to keep trimming the flowers until it gets bigger?
The onions I started later are taking off, too. I planted them as far apart as my instructions suggested, but I’m wondering if they need to be thinned out. The container is small, I know, but I’m hoping it’s just deep enough for them to succeed. I do worry if I’m keeping them too wet–the container is self-watering, so I’ve watered them less, but the soil is constantly moist. Will this be a problem later on?
My herbs (rosemary, dill, African and sweet basil, and peppermint) seem to be doing well. The African basil is flowering–do I need to cut these back for any reason?
My cucumbers are growing, but slowly. Three of them are definitely bigger, though one lags behind. I’m thinking the shallow depth of my bed is coming into play here. I wonder if I should try to transfer them to a deep pit like the one tomato I have already mentioned.
The four tomato plants I have in the bed, determinate and semi-determinate, aren’t gaining a lot of height, but they do seem bushier. Again, I wonder if the shallowness of my bed is already holding them back. Stakes and cages are in place for the semi-determinate varieties, but I only have stakes for my two Roma plants.
Here’s the peppermint I was warned would take over my bed given a chance. Do I need to go ahead and transfer it to a separate area or pot now?
My loose leaf lettuce seeds have sprouted, which is cool. I’m watching them closely to see how it grows. I didn’t fertilize these plants since they’re so young for fear of hurting them.
Also, the marigold seeds I planted along the edges between the mature marigolds I planted have sprouted, as well.
These pots are on the front side of my house. The small and medium size ones have more marigolds I planted from seed. I’m wondering if they’re getting big enough that I will need to thin them out.
The big pot at the bottom has Shasta Daisies. They took a while to sprout, and are growing much more slowly than my other flowers.
I’ve got two planters with Zinnias I sewed on my porch, and they’re really doing well. I’m wondering if and when I should think these too.
I appreciate any advice you guys may have as I progress. I’m trying to learn as much as I can, and you all have been an important part of my education so far.
If everyone is okay with it, I’ll continue to post updates. Thanks for your help!
10-10-10 is a decent spring fertilizer for a few reasons. Cool temperatures inhibit phosphate uptake in plants. So having some extra available when the plants need it helps with early growth. Also only around 1/3 of the phosphate in the fertilizer is available immediately for the plants to use. The other 2/3rds takes some time to change formulations and become available. After the initial shot in the spring a fertilizer that matches the plants needs is a better option. 3-1-2 NPK is not high N fertilizer. It’s balanced nutrition for the plant. The rest of the summer you’ll want to use it instead of the 10-10-10. The first nutrient defiency to show will be Nitrogen. When you see the oldest leaves on the plant start to turn lime green or yellow, give it some more fertilizer.
The tomoatos will set on their own if they are outside. Either the wind or pollinators will find them.
6 month potting soil usually has manure in it that breaks down slowly over time. Just keep an eye on it it might run out of nitrogen in 3-4 months.
You can add in soil to fill it up to the top. The leaves and such compact with water and will be competing for nutrients in the soil as they breakdown.
Prune the peppermint whenever you feel like it. I only do mine yearly.
Marigolds seed: If you leave the flowers and let the seed pods mature you can reseed them. Just wait until the end of the year and there will be a ton of them all over the plant.
Does fertilizer expire? If I keep this 10-10-10 for initial planting next year, will it still likely be okay?
On the marigolds, I’ve been deadheading the flowers when they decline and saving the heads. Will the seeds not be mature if I do that?
Would just straight compost with manure be okay to add at the top? I’ll want to rake out my mulch before I add it, right?
No it doesn’t expire and it will be fine for most of a decade.
The flower heads are the plants having sex. You have to wait at least 28-50 days for the babies to be viable before you harvest the heads.
Putting that much compost and manure on top will likely be way too much fertilizer. There’s a strong possibility of burning the shit out of your plants. Use soil. You can either rake the mulch out of the way and reuse it or add new stuff on top.