Thank you all so much for your advice.
I have booked them all in to see the vet....thats going to cost! I think I had better get them insured ASAP! lol
To answer the questions raised.
They are changed every other day, clean shavings, hay and straw, fresh food and water every day (bottles washed).
I give them 2 raisins each (I hand feed them so I know that they are not all being eaten by a just a couple of chins!), a small handful of oats, the other dried fruits I give are date, chopped small and equivalent of 2 raisins worth and dried apricot and pineapple (1 small cube...about 1 raisin size). I don't give all fruits every day, I vary it.
I'm not sure what plant the locust beans come from, I will try and find out. They are sold in packets (dried) as treats for all rodents.
The males and females are now separated. 1 of the females is definitely expecting and I think one of the others is too. I'm not sure about the 4th one. We are watching closely and continuing to weigh them weekly.
I believe they were being fed rabbit pellets in the shop (thats what it looked like), they are now being given quality chinchilla food.
Their poop is formed and slightly sticky to touch.
They have lava stones and wooden toys to chew as well as a chew stick (from a petshop) which is said to help keep their teeth trimmed.
It's been a very steep learning curve in the last 4/5 weeks! I knew nothing about chins when I took on these bundles of fur except that they needed sand baths....not a lot to base their care on! I have spent hours reading and trying to get it right but sometimes the sites give conflicting advice. Its great to have a place where I can get first hand advice while I'm trying to get it right