Sorry about the 3rd clown, but can't say I am not surprised --- there is reason it is recommended to keep only one pair per tank.
They aren't suppose to be, but all bets are off when a pair starts to spawn.
What other fish do you have in the tank? 1 total cube per day might not be enough.
My lights are on timers, the supplemental come on around 1 PM, off around midnight. The MH on at 4 and 4:30, and off at 1030 and 1100.
I wouldn't breed them to make a profit, I would breed them to learn and to help out the hobby. If you happen to make money great, but I wouldn't count on it. I have had clowns spawning in my tanks for about the last 14 years, never had the time to rear the fry, so good luck.