I have a reply from them on the cost, there is no minimum order.
Message me if you are interested, the cost is very reasonable, in fact cheap compare to the cost in Hong Kong, and they send worldwide, I don't want to post on this forum, without there permission.
Thanks @sdITBfanUK and @ShrimpNewb. For the last month or so the RCS and Darwin Algae Eater shrimp were growing and colouring up well with the small water changes I was doing. The water I have hovers around ph of 6.4 and I have Amazonia substrate. I thought the RCS were tougher than other shrimp and I know others have commented that the WP were closer to Caridina preferences. RCS are cheaper here, my LFS stock the plain red ones so I thought I would start with them. Anyway, will try smaller changes and dripping them in. It really is a balance isn’t it? Shrimp first or a lush planted tank first. Different requirements. I need to make a drip system for bigger changes. Thus far when I was “drip acclimating” the shrimp to put in the tank, I used a syringe over several hours. Dripping 6 litres by syringe might be rather tedious.
pH does seem pretty low. From what I've read, neocaridina like the pH in the low to mid 7s and struggle to survive below 6.5. I'm new to this hobby too and I would definitely listen to Simon, as he has given me a bunch of good advice thus far.
Also, when I was researching shrimp, I was advised to avoid planted aquarium ferts because they negatively impact the shrimp. That may be the reason for the deaths. Unfortunately, I know nothing about the Dino products, though I am avoiding Seachem Excel and the other ferts I normally use in my larger planted tank for the neocaridina tank. You may want to look into other ways to combat algae.
The water parameters are more caridina than neocaridina!
I wouldn't do a 50% water change unless really there was a serious problem. With water changes anyway it is best to drip the new water into the tank, this will also mean you don't need to worry about the temperature difference of the 2 waters.
Shrimps normally swim about more when you do a water change anyway, it also can trigger breeding and molting - I guess it would be the equivalent of heavy rain in nature!
You may also want to check the plant food is ok as they may contain something not good for shrimps, generally I believe it is better not to use plant feeds and don't use them.
Hope everything settles down and you don't lose any more shrimp.