Invertebrates And Soft Water

Hi all,
I did some routine water testing today, and found that the water from my tap is considerably softer than it used to be.
It was 7 KH and 10 GH. It is now 3 KH and 7 GH.  Oddly enough the PH is still 7.6. Having done a few water changes recently, my tanks now have the same readings.
I'm a bit worried about my shrimps and snails getting enough calcium.
I have 2 nerites and 1 yellow rabbit snail, and 4 amano shrimp in my community tank.
I have been feeding shrimp pellets every  other night and I have just ordered some snail pellets that are supposed to be high in calcium.
Does anyone know if the calcium and mineral blocks that you can get are any good? I've also read about putting cuttlefish bone in the tank or a liquid calcium supplement.
Any help would be appreciated.

I do indeed have what my water company calls moderately soft water. They give my GH as 85 ppm and 4.76 German deg. They don't give alkalinity now - what water companies call KH - but their last table in 2010 gave my average hardness as the same as it is now, and KH as 83 ppm, or the same as the GH.

I have nerite snails and cherry shrimps.
The snails do suffer a bit from shell eroison but I bought some of them as long ago as July 2011 and they are still alive.
When I first got the shrimps I did have trouble keeping them alive but a shrimp expert member on here helped me through and said my GH was on the lowish side but still OK (It was most likely a shrimp specific bacterium that caused the problems)


If you do find the shrimps and snail suffering you can use cuttlefish bone to give them some calcium. i've also seen Tums indigestion tablets recommended - but I don't know if they are available in the UK.

I don't know how accurate the information is on the MA site with regards to yellow rabbit snails, but it says that their water parameter requirements are quite soft water (<8 german degrees) with a pH of 7.5 - 8.5, so it looks as if your water isn't far off what is required to keep it happy, even without the Tums (unless it gets indigestion) 
It might be worth having a look at a snail-specific site to double check.

I don't actually keep invertebrates but I do have very soft water, hardened slightly by having some limestone/Tufa rock in the tank. Hope that suggestion is helpful. 

Sorry @fcmf, I probably got confused with Fiona.

Mine have updated too.  Now showing as moderately soft at dGH 4.62.  But they seem to only count calcium in that figure.  Lucky that I've got a KH/GH testing.

You missed TDS (total dissolved solids).  Around 4.62 does sound right for the KH but the dH will most likely be around the 8 mark where it's always been.