Suppose the coins are fair. Then we should get probabilites same $(0.25)$ for all the four cases. This is not true.
Now, we have $H_RH_S = 0.28$ and $T_RT_S = 0.18$.
$H_RT_S = 0.30$, meaning when $R$ gets head, probability of $S$ getting tail is more than $S$ getting head. $(\because H_RH_S < H_RT_S)$
$T_RH_S = 0.24$, meaning when $R$ gets tail, probability of $S$ getting head is more than $S$ getting tail. $(\because T_RH_S > T_RT_S)$
So, coin tosses are dependent and both the coins are not fair.