That’s probably okay then. My only other thought was that you might have too much light or too close to the seedlings, but 300W at the distance shown in the pic should be fine.
You may be right about seed quality. I don’t know what I was thinking when I said I don’t use seed banks, I have done, mostly from crop king seeds. I’ve bought good stuff from them until this year, when only one in five seeds germinated.















