In short, -raka and -yaka are compound of -ra + -ka and -ya + -ka, respectively. -ra, -ya, and -ka are all derivational suffixes that add a stative sense.
-ya is rather rare. In the Old Japanese corpus, I can only find three words: nikoya, nagoya, and fuwaya. This suggests that suffix was of only limited productivity then and explains why it was soon supplemented by -ka resulting in -yaka.
-ra attaches to adjective stems, nominals, and sounds. Ex: akara, mahora, simira, utura. During Old Japanese, more productive than -ya, but that declined as time when on. This too was supplemented by -ka resulting in -raka.
-ka Derivatives are often adverbial or the stem of 形容動詞. Ex: isasaka, oroka, sayaka, sizuka, niwaka, honoka. This same -ka is often attached to -ya and -ra.
Also note that there are two other related suffixes: -sa and -ma.
-ma: Attaches to adjectival stems, nominals, the irrealis form of verbs, negative -zu etc.
awazuma ni, kaerama ni, kotosima, sakasima, futuma ni, yokosima.
-sa: Attaches to adjectival stems creating nouns. Still productive. Rarely also attaches to nouns as well: tatasa, yokosa. Also joins with -ma to create -sama, which suggests an intriguing etymology for 様 (sama).