are the rodents drinking from the new valves? If they are not drinking from them...that could be a problem. Also did you rinse out the pipes etc before putting them into service? The tubing and valves may have grease or mold release on it which could be toxic.

Make sure your rodents can easily access the sipper valve as well, if its too high, they won't be able to get to it.

If its just the rodents in the tanks which still have water bottles only, and they are dying, then I expect your water bottles need refilling, or are leaking if they seem to run out of water extra fast.
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PHLdyPayne