After just losing two newly purchased LPS corals, I checked my alkalinity level and OMG is was 10-11dKH

I'm struggling with my pH at a constant 7.8 but have been unsuccessful to try and get it raised. My salinity is 1.022 and temp 76-78F.

I purchased this tank 5 months ago from an individual that had it as MDT for 2 yrs but wanted to upgrade. So I took original water, LR, and sand bed.

After 3 weeks of cycling it and gettig my water parameters, I've since added one occ clown, one coral beauty, one BTA, and two candy cane frags. Also have 5 peppermint shrimp, 4 hermit crabs, and a few snails.

I just need some help and guidance I guess. I get so many different things told to me by a few of my LFS.
What's the safest and less evasive way to raise my salinity, pH, and lower my alkalinity?

Thanks so much

46G Bowfront
40 lbs LR
Coralife 36W and 36W acantic, LED strip
Aqueon 55 filtration & one powerhead