Yeah, did you change a light bulb ever week or two, or did you change them all at the same time? You should have only changed one bulb out at a time. The burn-in intensity is about 120% of normal for the first week,... and decreases a lot after that over time.
(That's why I am enjoying LEDs so much, is that you can pick their intensity levels...)
That's good news about the clam. I'm sure it's loving all that additional light. What type of phyto are you currently feeding it? Iso, nanno...?
I replaced 3 of the 6 bulbs. As for the clam, I don't intentionally feed it at all. I have a lot of pods on my glass almost every day and when I clean the glass with my magnet then they get pushed off and circulated in the water. My clam's in current syphon/ mouth opens right after I clean the glass.