5htp is safe. Even in high doses its never caused anything more than an upset stomach(at least thats all ive read). L-tryptophan, a while back was pulled off the market due to a tainted batch(due to processing) that was released by some chinese company. Apparently it got some people very sick. Ive read its now entering back into the market.
B6 is also very safe. Ive read it can cause some problems to your cns(numbness) in very high doses(1000mg or more) but when discontinued these adverse reactions go away.
As pointed out, I would read the labels and take only what they suggest. My bottle of 5htp recommends 50mgx3 per day. My b6 recommends 100mg per day(tho I personally take more and its never caused me any problems).