You can via policies govern how much and how varied food is for various security sectors of prisoners. You can also mandate more eating times in the day, or longer eating periods. I TEND to do 3 hour periods through the day. Also look at distribution and check food distr. to see which kitchens are supplying which places to eat. May want to fine tune that or have some kitchens closer to staff canteens/prisoner canteens etc.
Also more chefs can help, they have a lot of work to do including running to deliveries to get resources, moving food to the canteens, as welll as cooking. Ensure quick flow from deliveries to main kitchen to nearby main canteen.
Also for people in solitary/lockdown your guards will attempt to run food to them during food times but again its a large fragile system. Ensure enough staffing in all these places, enough time and reasonably fast paths. Always helps me to run a permiter wall (or fence/wall at first) 2x2 path along the exterior of your prison and try keep that secure for staff to move around at speed and quickly access the kitchen/deliveries/staffrooms etc. Whilst all the prisoner stuff is on the inside of this walkway which allows quick access. If your prison is slow and convoluted and staff are constantly waiting for guards to open doors for them, problems. Equally same can go for traffic backlogs slowing inflow of raw material to the prison.
Any ideas specifically whats causing your issues?