RCS abnormal molting - how to increase GH safely but as quickly as possible

[RadiantStarr]

Yesterday, I came to own 15 RCS since a friend of mine was culling her colony (safely drip acclimated). This was pretty sudden and while I happened to already have a fully cycled planted 5.5 gal (betta recently passed), my city's water is known for being very soft. And after researching, I know that's a problem for shrimp and can cause molting issues.... which I'm seeing now (see attachments - not my photos since I can't get a good picture but these are pretty close).

Parameters:
Tank Size: 5.5 gal
Ammonia: 0
Nitrites: 0
Nitrates: 5-10
Temp: 78F-80F
ph: 6.6
gH: 3 (drops?)
kH: 2-3 (drops?)

I've crushed some cuttlebone and placed it in the filter and I got my hands on Seachem Equilibrium today. By my calculations, it's about 1/8 tsp to increase the gH by 1 for a 5 gallon tank. My question is, how quickly can I raise my gH in a safe manner? I only have one shrimp with molting problems right now and I assume it's too late to save it. But I'd like to prevent any other shrimp from developing the same problems.

[Autumnsky]

Replenish by Seachem and a product called salty shrimp, either would do similar function for water.

What is their diet also can be a part of the problem.

[kashif314]

As said use salty shrimp or liquid reminilizer like sl aqua blue wizard. It wi increase your gh to your desired level.