I'd say that would be a good guess, that's it quite a swing in PH, but most likely the peppers got burned from such a low PH. Lets see what some of the other members say...

-Eric
TechnologyGarden.net

Hi Eric,

Thanks for that, I think it must be that too. The only wierd part is that the plant were fine at ph of 5 or so. Do you think the plants will adapt to the new PH, or is this a late onset of PH burn?

Please excuse all the quesitons, this is my first grow in hydro :).

I enjoy your site by the way, have read it often.

Thanks a bunch

Travis

Yellowing between the veins could also mean a magnesium deficiency. Add a bit of Epsom salt to see if that makes a difference.

i'm new to this whole thing myself and i've encountered the same exact problem. except perhaps on a grander scale.
i haven't found a solution yet. and i'm loosing plants.
i have been having problems with the nutrients that i have been using, causing my PH to go down to 4 sometimes. i add the ph up but i hate fighting chemicals with chemicals. when i adjust the ph to 6 it will be at 4 in less then 24 hours. i figured shock was my problem, none the less, i had to transplant to a bigger container. next day rolls around, she's wilting and turning dark. 3 days. dry as a bone not sucking up water. i think she's a goner.
i'm going to keep an eye on this forum for a solution if anyone has any. though i might have done it myself with the transplant, i can't keep the ph up.

Try this:
Grow one or two "test plants" in an organic nutrient. I think you'll be pleasantly surprised.

I have some experience not sure what type hydroponic system you are using...? I am using a NFT system, I had a sudden fall in PH I kept using 'PH Up' the next day back down... I did lots of research, I discovered I had an anaerobic bacteria (not enough oxygen for the roots) the roots were brown not a bright white like they should be and the leaves were dropping badly. Several factors; left old nutes in too long, the NFT water level was too deep stagnant water(drain tubes not deep enough). I ended up replacing water/nutes and adding H2O2 (hydrogen peroxide) and continue to use H2O2 once a week and have never had any more problems. I change water and nutes every 30 days. I'm on my 3rd batch of lettuce. I have a very happy hydro system.

Here is a link that might be useful: My Lettuce Machine