The eye to body height ratio doesn't look bad, so I'd say they're not yet stunted. Keep up the water changes and cleanup after feeding and they should do well. The usual guideline around here is 10 gallons for each adult fish. Yours are juvies, so you could put in more while they grow out, but of course the bio-load will be higher and you might need to change more water. It's also recommended to quarantine new fish for up to six weeks before mixing with your others, so that's a consideration too. I think you've got a good number there already.