I have been growing these plants for a while when suddenly their leaves started to curl up, slowly. Is this a sign of root rot? Should I replant with some perlite added?
It seems to be getting worse :/
Gardening & Landscaping Stack Exchange is a question and answer site for gardeners and landscapers. It only takes a minute to sign up.Sign up to join this community
Actually, your pepper plant does not look too bad. It is about to produce a pepper, and the leaves do not show obvious deficiency of any kind. It may be a bit lanky and soft, but the irregular corrugations on the leaves are somewhat normal for peppers - just look at online images for "chili pepper leaves" to see what I mean.
There is a previous question about chili pepper health that you might want to peruse to see if the question and answers are relevant to your situation.
The one leaf in the centre of the image which has rolled over on the right side is calling for investigation to see if an insect has made a home inside the roll of the leaf. If so, rub it out carefully and continue to watch for repeat attempts.
Your soil looks a bit peaty, but evidently is sufficiently rich to do the job. Leaf corrugations are somewhat due to irregular growth, but also dependent on the variety of pepper. Some varieties have very flat leaves. If your plant is a Cayenne then that would be unusual corrugation in my experience. Try to increase light levels to the plant, and ensure that growth is as regular as possible.