So this mornin my shrimp was doing good, then I looked 3 hours later and he is on his back twitching fluttering and about to die. He even lets me grab him to put him upright. He just molted like 3 days ago too. What is happening please help!!! I have a 20 gallon long and a good amount of rock. Parameters are all good ammonia 0 nitrite 0 and nitrate 20 going down. Im gna do a water change soon. Please help!