You said 5 m/hash. For 1.5 m/hash that's to be expected.
This is one of my two rigs. The second has 3600 kh...
Yeah but you cant put em together as one when you solomine. Diff is abit higher now as Nullu said so can take a while before you find anything.
Might be better off just getting both rigs pool mining on one account. You'll probably get roughly the same amount at this difficulty, maybe a little less, but the supply will be steady, and won't require luck.
I usually solo mine for a day or so, then switch to pool mining and see which gives me the best share based on the difficulty.