Alk spike problem

Hi all,
I have been having a spike in my alkalinity recently (which I think is due to doing 2 large 50% WC after aquascaping and trying to revive tank after some neglect). The tank has a few fish and soft, LPS SPS (acros, staghorn which seemed to be doing well before alk spike)
Parameters:
- Tank set up for almost 2 years – 40 gallon long tank
- Temp: 78
- Salinity: 1.025-1.026
- Nitrates: 0-5
- PH: ~8
- Phosphate: less than 0.10
- Magnesium – 1300-1400
- Calcium (400-420ppm)
- Alkalinity – used to be running it 8-9 now it spiked up to 10-11
- Using Instant Ocean reef crystals
- Dosing: I have been dosing 2 part and i think part of the problem is that i should have turned off doser after those 2 large WC but i didnt :bawling:
Damage:
- lost 2 acans which i though is due to making water a lot cleaner after water change but i guess it was due to alk spike
- Acros have started RTN i lost like 2 small frags and staghorn colony is started to slowly stn (like .3-.4") at the bottom.
- even poccillipora seemed retracted for half of the colony yeterday

What i have done so far:
- turned of all dosing, not doing WC until things stabilize (reef crystals has alk of 11) so i think wc will make things worse.
-as of yesterday slowly dosing calcuim (like 3-4ml) in an attempt to drive alk slowly, will test every 24 hours. I know that my calc is fine but i thought i would push it slowly up to bring alk down gradually.

all input welcomed
Thanks