Biggest mistake what you can do is to DO thinks without thinking much.
First , most of the people who created PRL and PBL lines have their shrimps in PH 5-5.5
I have all my PRL ,PBL and TBís in PH 5.2-5.7.I have random dead too. Especially my berried females.
Some babies have hard time to make it too but I still growing and multiplying my population.
I start with GH 4 now Iím at 6 still not much improvement. My WC are 10-12% every 2 weeks.
Interesting is that any kind of supplements like Mosura: mud,tonic pro,white, BW :gravidas,TB-9 ,BW stout,shield are triggering problems and there are much more dead shrimps.
Something else strange to mension. Last summer I tried for 4 months little experiment. Month 1 GH4,next one GH6,Month 3-GH4,forth FG-6 again. WC was done for 2-3h with slow pumps. In those
4 months I have very few dead and a lot of berried and babies.
My RO come PH6 if I keep it the bucked for 2 days PH become 4.8.
With New Amazonia tank only I easily can have PH 5,5 with RO water changes only.
For RCS go for PH7 and up.