If your numbers are accurate, then your chlorine is no where high enough to kill algae. With a CYA of 90 (and by the way, you do NOT need to test this daily as it won't change that quickly and will just waste testing reagents), your shock level is 20ppm. But, if you truly do have mustard algae, your shock level may need to be even higher. But, since you haven't been maintaining consistent readings of 20, I'd try that first before deciding to go higher. Again, the chart with the CYA/Chlorine connection is here:> http://pool9.net/cl-cya/

Keep the chlorine at shock level until you meet these 3 criteria:
1) You lose no more than 1ppm of FC from sundown one evening to within an hour of sunrise the next morning
2) You have no greater than 0.5ppm of CC
3) Your water is clear and no patches or spots of algae anywhere

At that point, we recommend keep the chlorine high for at least one additional day and then let it drift down but never let it drop below the minimum from the chart which is based on your CYA reading.

I would NOT use a floc at this time. There is no reason to. I think your problem is that you haven't killed the algae because of inadequate chlorine levels.