hmmm, thats really strange! besides for the usual nutrient levels check, i would question whether they had too much or too little flow. I have placed mine in the bottom third of the tank, and they seem to be flourishing there. Im not sure what else I can tell you... I would highly recommend dosing. I dose Calc/strodium, Mag, Alk, nitrate remover, phosphate remover, and trace elements. I also run a small fuge in the sump with LR and some macros. But i find that dosing has allowed me to keep my levels spot on, and can minimise the need for water changes to about every 3-4 weeks. Keep an eye on the hem tho, if he starts to deteriorate he will release toxins into the water very quickly, and thing can go very bad very quickly! I hope things go well from here on in! do you use a filter sock?