SR NAND and NOR Flip-Flops
As suggested in the comments, for the NAND RS Flip-Flop, consider inverting the R and S inputs.

Additionally, it may help your understanding if you consider the SR NAND flip-flop with the deMorgan's symbols for NANDs, emphasizing the active input negative state.  



Either input 0, causes a 1 output. 

On the SR NOR flip-flop, either input 1, causes a 0 output. 

If you compare the two flip-flops, the logic symbols are now forms of OR's (one a negative-OR and the other a NOR).