Need help with my water Balance

[basestring]

Hi,

I'm new to this forum and to keeping a reef tank
I'm doing it now for 3 month and it's not going as it should be
2 days ago I lost my Blue carpet that I bought healthy as far as I know and read
I also lost 2 clown wish, 2 damsels
The rest is doing well.

My PH is way too low 7.6
the last view days I'm trying to play with the calcium and Kh

When I started, the PH was 7.8, Calcium was 240 and KH was 12 dkh.
as you see the Calcium is way to low and the PH is also a bit low.
I don't have a Calcium reactor, but I bought Kent Calcium supply and seawater KH Balance

In the last 3 days I worked the Calcium up to 350, but my KH went up too
and is 14 dkh and my PH dropped to 7.6

Here are all the test result that I can do

PH - 7.6
salinity - 1.023
Temperature - around 25C.
KH - 14 dkh
Calcium - 350
No3 - Around 25
Ammonia -Between 0.02/0.05 ppm(save)
I also Have a Phosphate tester but don't get any results

It's a 500 Liter reef tank
with a skimmer, Cotton filter, 100meter no3 filter tube that drops 1 drop every 3 seconds , and self-made Bio filter with around 10kg white looking round stones with a hole in it. I forgot the name the packing had only Chinese text, can't read Chinese yet!!! and I've a 9w UV lamp

I also dose 2ml vodka daily

Any suggestions?