Hi Sue, and welcome to the forum - though sorry you have become a member of the "RA Club!"
I have been on two of the drugs you are on - MTX and SLZ - and certainly the MTX affected my taste buds. There were some foods I simply could not tolerate at all, which pre-MTX I enjoyed. Also, I can identify with the metallic taste in the mouth - I used to use a minty-flavoured mouth wash, if I remember rightly. MTX and SLZ didn`t work out for me, and once I had come off the MTX I regained my normal appetite for all the foods I`d enjoyed in the past.
If you were diagnosed in July I suspect it may take a while longer to assimilate the drugs, and for your body to get used to them. If things don`t settle down you could perhaps speak to your rheumy nurse, or whoever is monitoring your bloods, and see what they advise.
Take care,
Kathleen x