Definitely too crowded. Snip off 3, leaving the healthiest one. As you indicated, it's a little too late to expect much recovery but you know for next year. Also, 5 hours of sun is rather limiting. Can you put them in a sunnier spot?

How long ago did you put them where they're at now? I'd say snip all but one, like slimy said. But if you transplanted very recently, you can probably still divide them.

If so, let me know and I'll walk you through on doing this.

Kevin

I would say, just leave it as it is. At this point in game is too late to change the rules.

The clumped thing will produce more than if you just leave one and kill the rest.
Because there are several plants, I would fetilize them more often, with weaker dosage( maybe 1/3 recommended strength, maybe once a week). As long as there is room for the roots to spread and they get nutrients, it should be fine.

The advice from seysonn is good. Definitely not classic proceedure, but it will probably maximize your yields. I would prepare some manure tea and apply that every three or four days. Just get some good composted cow manure, add water, steep until good and brown, then water with this tea. This was a technique used by the famous organic gardener, Alan Chadwick, at the University of California in Santa Cruz. See the link below for more information.

Here is a link that might be useful: Alan Chadwick

I too agree to leave them alone. If I'm reading the conversion chart correctly, the temps are between 64 and 77 degrees Fahrenheit. A bit on the chilly side for a chilli! Also 5 hours of sunlight is considerably less than what they need. If they are fed and watered, you will still get some fruits, but nothing close to what the plants are capable of. it is also likely they will not be as hot as they could be either. Fish and seaweed emulsion will also work well as a supplement to the nutrients in the soil.