I am not sure what critters were under the pot, there are many harmless ones that would be attracted to the moisture and sun protection. You can place the containers on wood/brick pieces to elevate them an inch or so off the ground to get rid of them. If it was the bottom most leaves that fell off those were almost certainly seed leaves and it's normal for those to be cast off some time after true leaves form so no worries there. Cukes grow a lot faster than peppers so I wouldn't be too concerned about them in this case. It takes a lot more predation to bother them than the slower growing peppers. Probably a good time to head to the store and replace the peppers that are just stems. If they survive then you have bonus plants :) In the case of the disappearing leaves or half gone leaves I would be looking for a pest as the culprit. May have already moved on, if you are lucky.

It's not necessarily the peat that is the problem, but the pellets are encased in a netting that can inhibit root growth in spite of what the manufacturers say. If you use them to start your plants, cut and carefully peel the netting off when you pot up or transplant to the garden. Don't use 'garden soil' as it will carry bugs and pathogens that can kill your seedlings. Straight peat can compact, dry out and crust up, or hold too much moisture...starting mix has peat with vermiculite and other stuff(perlite?)mixed in. It is also sterile. I use Jiffy starting mix in cell packs, then use potting mix when I pot up to 8oz cups after a few sets of true leaves. As for peppers, you can find a lot of info perusing the Hot Pepper forum(growing info applies to sweet peppers too). There will be as many different methods as there are posters, and no way is THE way. What works for one may not work for another. Don't forget to read the FAQs at the top of the forum page. Peppers seeds need warmth to germinate, about 85 degrees is ideal, but they will eventually sprout at temps a bit lower. Keep the medium moist, but not wet. Some varieties will take longer to germinate than others and I've found it's best to keep different varieties in their own cell packs or pots so you can take sprouted ones off of the heat without disturbing the others. Don't fertilize your seedlings until they have a couple of sets of true leaves, and then do so with a very weak solution. Also, you don't say where your location is, if you're starting your seeds indoors, what kind of light source you have(lights, bright window?)and that info would help with feedback. Hope this gives you a starting point. Here is a link that might be useful: hot pepper forum

Of course you can make it any size you see fit, and using any materials that are easily available to you. Though I think 6 inches wide will probably do, I would opt a little wider 8-12 inches wide. Here's how I planed to build mine. First plywood would be stronger, but OSB board would be cheaper and still strong enough. It runs about $7-$8 for a 8x4 sheet around here. I plan the inside diameter to be 12 inch deep, about 12 inch wide, and 8 feet long. Make it as long as you want also, 8 feet is all I need. Though I plan to build 2, set them parallel with each other about 5-6 feet apart, and place a A-frame trellis between the two trenches. You already have your trellis. To strengthen the box structure, I plan on running 1x2's (they run $0.84 ea here) along the outside for added support. You can use 2x4's but would be about 3-4 times the price, and 1x2's should be enough support. For a trench box that long, I would probably run one horizontal row of 1x2 along the top and bottom of the box. Then periodically place vertical pieces between them. Here in the desert I need to insulate the roots from the heat, you probably wont want to do this part, especially if you are going to have the trench in the ground. My trench is planed to be on top of the ground. The inside of the box will be lined with probably 2 layers of 1/2 inch (or 1 inch) thick Styrofoam sheet insulation. Glued in with PL300 foamboard adhesive (it's made specifically to glue Styrofoam insulation to wood and construction materials. Then I plan to line the inside with vinyl sheeting. I don't know if Low's or Home Depot carry it, but ACE hardware just down the street from me does. They have 3 different thickness that run from about $3-$6 a square yard (in one yard widths). For the inside diameter I plan, it should just fit nicely without even overlapping it (except the end pieces. I plan to use 100% silicone to seal the ends and glue down the vinyl sheeting (as well as all corners and edges after the Styrofoam is glued in). Fish pond liner would be just fine, and plenty durable. I don't know how much it runs, but I think I will look into pricing that as well. For the drain I plan to cut a hole just big enough to run a pvc tube through the wood, and a little smaller than the wood hole in the Styrofoam (for a snug fit). Then glue it to the Styrofoam with the foamboard adhesive. Then run beds of silicone, and screw in a pvc connectors on both sides of the tube and snug it down. Making the lip of the connector on the inside of the box as short as possible (but still durable), so as much water will drain out as possible. I may decide to have more than one of these drains per box. But if one side of the box is raised a little, the water should flow nicely to the side with the drain/s. Because the heat and sun is so bad here on things. I plan to paint the outside of the box with a roofing material. I forget what it's called, but it's white, thick, durable and flexible. They use it on rooftops for reflecting the suns rays (overall cooling the building). That will also add another layer of insulation for the roots for me (reflecting the heat). But I need to find somewhere where they sell it in one gallon buckets. The 5 gallon buckets are way more than I need, and it's not exactly cheep (a one gallon should run about $10-12). That should protect the wood from moisture if you plan to bury it in the ground as well. However there is another material for that also, but it's black. I forget what they call that also, but they use it to protect walls that extend underground so they don't absorb moisture (like basement walls, underground stairways etc.). I don't know how much it runs, but you will want to protect the wood from ground moisture if you place it in the ground. And products like Thompson water seal wear off and need to be reapplied regularly. Once the box is ready, I plan to simply place a section of inexpensive furnace filter screening ($2, I just cut the screening material out of a inexpensive furnace filter) on top of the drain holes. Then I will place a layer of rocks on top of that to about 2 inches deep along the bottom of the trench. This will hold the screening in place and help with drainage all the way through the box. Then just fill with the growing medium and plants, setup the drip system. You should have a very durable planter box that will withstand the weather and you can use year after year. .

I followed instructions found somewhere in this topic last year to fertilize seedlings once a week with very diluted liquid fish fertilizer. I think it was one tsp per gallon of water instead of the normal one tablespoon. I put a general granular vegetable fertilizer in the planting hole when they are transplanted outdoors into the ground (so I'm planting where something else grew last year). I have added maybe an inch of composted cow or horse manure to the bed. The transplants get full strength fish fertilizer after I water them in. They might get a second dose a week later but that's it on fertilizing. Since I grew about 30 different kinds of peppers, there are some I will not grow again because they weren't productive compared to a different variety 18 inches away. If I weren't so negligent about fertilizing during the growing season, those poor producing types would probably end up getting too much fertilizer thinking it was needed.