I'm not sure if I can help, but we would need more information. How long have you had the bin; when did you notice any change; why do you think they are sick; what have you been feeding; is the bin too wet or too dry; and anything else you think is pertinent.
Kath

my 1st thought would be too wet

ONLY A FEW TURN GRAY. I HAVE HAD THEM FOR 14MONTH, THE OTHER ARE FINE & RED. A FEW TURNED GRAY, NO REASON THAT I CAN SEE.
THANKS

you're probably YELLING at them too much.

Sorry, Know really I am sorry
I have been on sites for about 4 months.
I keep forgeting that the Caps Lock is on.
My wife told me ALL caps mean I am YELLING, but I forget.
I am learning(it just takes some of us longer then other).
The hunt & pick does not help.
I will try to remember, thank you for yelling back. Oh I do not know what to tell you about the worms. they are happy, even the few Gray ones. If I find out why I will Let you Know.

One possibility is that at some point you have somehow got some egg casings from a common earthworm species such as Lubricus terrestris mixed into your bin environment - did you put any garden compost or soil into your bin at any stage?

Here is a link that might be useful: Earthworm versus Redworm

Could they be pot worms?

Pot worms tend to be long, thin and more white than gray. If only a few are gray I want to say don't worry, even if you lost a few, once you really get going they reproduce so quickly that you will eventually not care (some people care about each worm but I'm speaking in general terms).

I use a stacking bin system and at first was really careful not to squish any when looking through the trays and putting them down so I could poke through the tray below. Now I am somewhat careful but there are so many and they reproduce so quickly that a squished worm now and then doesn't phase me. I don't go squishing them on purpose but sometimes you can't help it. As Spock says, "The good of the many outweighs the good of the few ..."

I have at least four(4) different species of worms living together. I only bought "Red Wigglers".
Maybe the gray worms are a different type of worm and they share the space with the worms you bought.
By the way, I think a "mix" of worms actually do a better job of composting because each type of worm has different tastes and talents. They also have different needs but they are all proven survivors.
Good Luck with them worms!