Photos are needed. Try get some close up detailed shots.
Emersed grown HC sometimes melts after being submersed (which is something that nobody tells you before you set up a dry start).
The blackout might have helped the melt begin. Also, while 11w might have been enough before in the dry start setup when you submersed the plants the light is filtered and reduced by traveling through the water. This means you need more light to keep the same plants alive.
Will need to see photos before saying anything definite, without seeing photos everything is just a conjecture.
Emersed grown HC sometimes melts after being submersed (which is something that nobody tells you before you set up a dry start).
The blackout might have helped the melt begin. Also, while 11w might have been enough before in the dry start setup when you submersed the plants the light is filtered and reduced by traveling through the water. This means you need more light to keep the same plants alive.
Will need to see photos before saying anything definite, without seeing photos everything is just a conjecture.