Your water parameters are fine and there is no reason to purchase an ro unit. GREAT NEWS
We probably need a little more info to shed light on the recent death.
How long have you had the rcs? 1 month
Have they been molting normally? yes
Are there fish in the tank? no
Are you running co2? no
Have you recently dosed any products that contain copper? nope
How do the rcs behave? eating moving flying around at times
What have you been feeding them? they dont eat anything i feed them. but it has lots of plants and moss
you don't need one because you're KH/GH are fine, along with the rest of your water params, no need to spend the money if the water is coming out like that. But if you're KH/GH were both, for instance, over 8 or 10+(Hard Water) or something, you'd probably want to get it to soften the water and bring the TDS down. You already have soft water in the range that the shrimp likewhy does everyone say ro system is the best and a must!!!!
why would i not need one ?