Seeking advice - plants look very dehydrated, but that's not it...

So I'm looking for some advice here and am hoping some collective wisdom could help...
 
A number of my plants have all of a sudden decided that they are not feeling well, really unwell. And it happened quickly, over the space of 1-2 days. Outwardly it appears that the plant is suffering a shortage of water, and this seemed a fair indication given that the first instance was during the heat of the day, when a little leaf droop is not unexpected. But then it continued.
 
The plants are in pots, likely too small but I've not really seen this problem before. Initially I thought they were short of water so of course watered them a bit - no help.
Also I thought they may be suffering root rot through over watering so transplanted one, but it's still not doing well. (This one is hard to tell because transplanting something at any time leads to a time of getting back to a semblance of reality.)
 
They were Espelettes and red habs, although I think 7 pot primo could be showing signs of issues but is still doing OK. I'd post some pictures but there's not much to show other than a plant looking extremely dehydrated and otherwise no signs of leaf discolouration, etc. They really were in fine health - good growth, fruiting, etc. - to this point.
 
Thoughts? Much appreciated in advance.

have there been any changes made? recently fertilized? moved to new location? drastic weather change? when you repotted the one plant did the roots look ok or did they look rotted? overwatering is one of the most commonly seen problems with peppers. pictures may help someone here tell you what the problem is. 

If all plants are suffering the same ill, and there's no pics posted, then the no pic diagnosis, is that you're watering too much, and/or it's wilting in the midday heat.

So just wanted to give an update here and thanks to the advice received. Indeed it was over watering on my behalf. Interesting that the visual indication of over watering is an extreme version of a plant looking dehydrated. I guess that is indeed the case - the root system shuts down and the plant get's no hydration / nutrients.
 
Thinking back there were no changes other than the weather: in June and July it was extremely hot here and the plants were loving it. Of course needing quite some watering. I was checking the pot weight and certainly no over watering. But then the temperature came back down to more normal summer weather, yet I continued to water as before.
 
The plants are still going although quite a bit of die back. And I'm more careful now with the watering!