The brown is not a discoloration; mine do that, too, some varieties more than others. The stem tends to get woodier as the plant matures.

Where are you located? Peppers like their soil warmer than say tomatoes. That wood mulch may be keeping the soil from heating up as much as the plants prefer. Also the mulch insulates the soil well enough that the soil moisture may be higher than you think, so you may be overwatering slightly.

Did you fully harden the plants off before planting out? What have your high/low temps been like since you planted out? What kind of soil did you add to the bed? To the pots (not regular garden soil, I hope)? If you have fertilized, what and how much? How often do you water and how deeply?

If the days are hot enough, pepper plants may droop a little but should perk up once it cools off. You might want to think about some sort of support for the plants before they start getting larger.

What I see on your picture seems perfectly normal. Dark purple colouring is usually from anthocyanins, a pigment found in lots of plants. Peppers often get it on their stem and at the junction of shoots and branches, even on leaves at time. Your plant looks healthy IMO.

What happened to you plants last year sounds quite different and was and actual problem, too bad they died from it, but that's in the past and now's a new season and you seem to have a good start!