Good to see you are looking at feeding schedules and are concerned over weight gain.
They need weekly feeding when they are growing but once they hit about 800g I'd cut back feeding to once every 10-14 days.
Weigh your balls after they poop, this will give you a more accurate reading of their weight. Weight gain of 50g a month is imo a healthy gain, anything more would indicate that the fat reserves are building up too quick.