Wow Marc,
Sorry to hear. Seahorses are really challenging IMO. I have had mine breed on a few occasions and raising the fry is incredibly difficult. It is, however, incredibly rewarding.
And as a side note, I keep them in a 29G ( 100G tottal system volume) and the tank is not the required 3 times taller than their bodies with extended tails, and they still breed.
One of my H. erectus currently has popeye, so if anyone has some ideas on treatment, please let me know.
I currently have her in a 5G tank with a little bit of live brine and am medicating with melafix.