I think the real problem is not just the developer because you are getting lower speed than what Microphen should get.(posted 8163 days ago)However, HC-110 is the developer that even Kodak implicitly (or explicitly but in indirect words) admitted that it can't deliver full speed with TMY though they claim to deliver rated EI400 with D-76 and other standard developers.
I'm confused who was using 35mm only, but I didn't like HC-110 for 35mm after using it for a while. It looked pretty nice with FP4+ but then I don't use FP4+ any more. I still have some five-year old HC-110 left in my shelf but I don't use it except for APX25 in 120, which isn't a bad combination. Don't you think you'd be happier if you find something that works even if you are never going to finish your bottle of HC-110??