Why does my pepper plant have yellowing, drying and curling leaves?

Question

One of my pepper plants has so far suffered from pests, blossom end rot and odd skin blemishes and unfortunately the plant is now taking a turn for the worse and looking rather unhealthy.

The leaves are drying out and curling along some edges, and they aren't very green (yellowing?).

The unhealthy plant:

You can see the largest dry patch in the first image - the front of a leaf, while the second is the back of a leaf to demonstrate the loss of colour - compare it to the shots below.

Another healthier plant (for comparison):

This plant sat next to the unhealthy one, about a foot away on the same window sill, so conditions should be very similar. Images are again front then back of two leaves.

A few other points that may be relevant

• This is an indoor potted plant, it hasn't been moved in months.
• Fruit has been produced and harvested (although the first few with blossom end rot, as mentioned).
• It's watered with the same regularity as its peers.
• Water isn't being absorbed as much as with its peers - more ends up in the tray underneath, forcing me to give it less water to avoid overflowing.
  This is unrelated to the issue raised in another question of mine - that was a different plant.

What could be wrong with the unhealthy plant?
What can I do to help it?

Answer 1

It looks like your plant is pot bound (also known as root bound). The solution here is to purchase a bigger pot or transplant it into the garden. Based on the time of year and the fact that its an indoor pot I'd say that a larger pot would probably be the best solution.

Mike posted some links to repotting that you can use to guide your repotting process.