I have 5 gal of cyser that isn't quite right.
I started with 9.5 lbs of honey 3 tsp of nutrants, 2 grapefruit pealed end mushed. water to 5 gal. I used red star champane yeast.
starting sg 1.040
after 2.5 weeks 1st rack SG 1.000
after 3 moor weeks 2nd rack mead is very clear . but tastes flat for lack of a better discription .
Should I add more honey and re pitch or just pitch?
Well repitching won't change much, since it's fermented mostly to dryness. Champagne strains will do that. If you were looking for a mead with some residual sweetness (and honey flavor) you'll want to stabilize the mead ansd sweeten after stabilization. Champagne strains also have a typically neutral flavor, so you probably have a dry mead which may have a pretty neutral taste, except for the young hotness which should mellow with aging. You call it a "cyser"... are you planning on adding apple juice later?
By my estimates your starting gravity should have been more like 1.068, but it's not unusual for some of the honey to not have dissolved completely unless the mazer takes some pains to do so.
My preference is to age a mead "as is" to let its true character come out a bit before starting to tweak the profile, but with a good palate and experience one can certainly intervene earlier if one wants to.
If it works out you are truly a great mazer. The fruit of grapefruit is a difficult ingredient to work into recipes.
Send some to me so I can better make suggestions.
Are you trying to carbonate?? or just get the tingle? If you want to carbonate you can "prime" and bottle with corn sugar. If your fermentation is off you can "fake" the flavor I think you are looking for by adding a bit of FRESH ginger and letting it stand for a few months. If you are going to to use ginger pe very prudent with the amount as too much can overpower any unfermentables that are left.