Hello, i have got an aquarium several months ago which came with this 9W fluorescent bulb not working:

The container which seals with plastic cover was 3/4 full of water which in my opinion explains half of it colored yellow.
I later replaced it with 15W fluorescent bulb which worked for a little over a month and today stopped working:

You can notice a little yellow color here as well.
Question:When lightbulb was on for a long time, i felt heat coming from plastic which also raised water temperature by 1C. Could water evaporation in bulb's container be the cause of bulb's malfunction or it was just bad bulb or 6 additional Watts output? The container's "ceiling" is shiny and i don't know if it is metal or steel, but it is burned.
This is how the container looks. You can see plastic seal as well:

I also want to tell that weeks later i have noticed that rubber which is placed on plastic cover had gaps on both sides and today i used white silicone to fill them with:
Question:I used silicone 8 hours earlier today and it still feels not that sturdy. Should i assemble plastic cover back or wait until silicone is fully sturdy?
Thank you for your answers beforehand.