Unfortunately very many people casually lump a huge range of maladies under the umbrella of "RSI" and treat them as if they all have the same root cause and the same remedy. Wrist/arm pain could be carpal-tunnel syndrome, or it could be tendonitis, or it could be any of a bunch of other things all of which are technically "RSI". For some, strength training can certainly help; for others, as in your case, it may do more harm than help.