I keep most of my sensitive Taiwan Bee shrimps in TDS ranging from 250 to 350 and they are doing great.
GH is more important than TDS. To be exact, it is the individual nutrient levels in the water. For example, Na, K, Ca, Mg, Mn, Fe, Zn, Sr, SO4, PO4, Cl, MoO4 and BO4. GH is a easier and cheaper method of measuring the meso minerals (Ca & Mg), however, it will not tell you the exact level of the rest of the nutrients.
If you are using RO replenishing minerals from respectable brands, be it it is for fish or "specialised" for shrimps, they should be more or less the same. The lesser the TDS the salts, the less substances are inside. In theory, it will be even more lacking in those nutrients I mentioned above. Most commercial salts are in the TDS race against each other. They accomplished this by using salts that has lesser free electrons, such as chloride. In actual fact, TDS does not tell you anything, except how conductive the water is. Generally, field scientist or I only used it to measure the changes to the amount of dissolved solid to detect overdosing, changes to ecosystem or pollution. The absolute value is pretty meaningless. As such, don't get too obsess with TDS. With frequent water change, your tank water's TDS should remain the stable from 1 month after you start up your tank till 5 years later.
One thing to take note about GH. The lower the pH, the higher the GH you will need; the acid will soften and wear out the shell faster. For example, you may need 6dGH for pH 5.8 water and you may only need 4dGH for pH 7.4 water.
Shrimp needs stable water parameters instead of the water parameters of other's tank. Hence, if the salts you are using are working fine with your shrimps, then just continue using it and avoid changes. If you are intending to change anything major, it is better you use it in a new tank.