They still don't "need" grain, but if you feel better giving to them just give a handful each. My don't have much browsing because well, they ate it all, so they have a run 24 feet by 50 or more long plus a large house, and two hay nets a day. The are happy and health, good weight. That is the diet they've had since we've gotten them, at a couple months old, (ones five years the other two are year an half still growing). The only time they need it is if they are dairy goats, than a ration would be needed or they are for market. A dairy ration shouldn't be fed to them unless pregnant of lactating because it isn't balanced for every day.
If they seem not to thrive if you take them off the grain deworm them with something like ivermecton, a couple of days in a row (horse tube wormer works).