DIY projects

so Im having trouble maintaining the temperature at 79 in my 55 gallon with 20 g sump with about 15 g of water in it. Im running 1 150 watt in the return section and 1 100 watt heater in the 2.5 refugium. and 1 100 watt heater in the overflow section of my sump am I better off having one heater or 2? or is more the better? should i have one in the tank?

I completly redesigned my sump and replumbed my whole system will post pics when its completly finished

Thanks ...

So ive convinced my self my tank just dosent have enough flow.... ive plumbed it with 1/2 cpvc and the pump im using is a via aqua 3300 which does 977 an hr but at 4ft head which is how tall my stand is. There are two returns that go into the tank on either side and the over flow is in the middle. The overflow im using is a is a HOB which does 600 hr, but because of all the right angles I have used in the 1/2 i dont thing there is even 600 going through there. Does anyone have any suggestions ...