Can I return newt larvae to tank w/ others?

I wrote yesterday about my oldest FBN/C.Orientalis possibly being upsidedown in the water amongst the plants as I could have sworn I was looking at an orange belly and thought he was dead. Then, he was swimming oddly and resting almost vertically. Well, since then, he's been fine. I had immediately isolated him and he seems to be eating - I'm introducing frozen small bloodworms and continuing on the other foods (Daphnia live and frozen, BBS frozen) and I'm hoping to add whiteworms (hint to Dawn!) soon. He is spitting some of the frozen bloodworms out - maybe they're still too big? Anyway, he seems OK as far as balance goes. I have no idea what was wrong if anything as no one seemed to have any thoughts. My new question is: Is it safe to return him to the larger tank w/ the three other larva his age? I currently have three baby tanks going to accomodate their different hatching rates...

Dana