Flowers, I think you may have answered the question. If you got these at sprouts, not really potted, meant to harvest until remainder goes in compost, could be a losing battle. I tried a couple of pretty mints a few years ago from Fresh Market, or somewhere, thinking I had struck gold. Wrong! All they did was go south on me.
Go to a garden center and get a few starts potted in dirt, ready for larger pots or ground. I don't know what your temps are, but both oregano and mint can take a light frost, perhaps down to 30 and still be pretty. If you see a chilly night, snug the pots up against the house and sheltered. If cold, bring in! As you are drier and may be windier than here in the mid-south, will need to water more than I do. All of my pots drain, but I don't worry about lighter or faster draining soils. I've used Miracle Grow potting mix in smaller 10" pots that may be coming in for a couple months in winter.
Trial and error is part of the game and challenge.
Hope this helps.