Is that 30" from the sand bed to the actual "space" between the LED's and the waterline?
Also, how is the ambient temp running two of them at the same time?
perhaps your fish got stressed with the new shrimp tankmates which drove it to be susceptible to disease or lower immunity to it thereby killing it and in the process, your shrimps are just doing its job in nature, that is to scavenge... IMHO...