HELP!!

I came home to 2 dead fish today. My med. clarki and my domino damsel. No signs of injury or disease that I can see. They were fine last night at 10. Scooter and CB shrimp both sluggish, all other fish seem just fine, eating and swimming around.
 Tank has been up for about 4 months (transfered from a 55G that was about 9 mos old. ) I have a 135G with a 75G sump that has LR, crushed coral, chaeto and a Skimmer in it. T
 The DT has 1 rectangle trigger, 2 small false percs, yellow tang, a tiny blue and a stripped damsel, a threadfin butterfly (does not bother my corals), a small scotter blenny, small 6" snowflake eel, various snails and crabs maybea dozen all together (need alot more), coral banded shrimp, long ten. nem, pencil urchin,  pulsating xena, athenia, green and purple shrooms, yellow polyps, hammerhead, a couple sps. 130# LR, 2" sand bed of crushed coral. 2 korillas, it has dual drilled dursa overflows, 72" t5s 10k/act.
Temp 78.1
salt 1.025
amo. 0
trites 0
trates 20
ph 7.6 just added buffer
phosphates 20 battling a little hair algae
Any clues or suggestions, I have had them both for almost a year!!!! I also, bought a 2" LMblenny to help with algae and he died a day later??? That was 2 weeks ago.
Here are some pictures if it helps.
Sump 1

Sump 2


Nem and tang seem fine.

Corals and other fish seem fine.

He is usually VERY active and has not moved since i bumped him to see if he was alive.

He usually darts away from me, now he just slowly walks away???

he looks fine

they look fine

 

Forgot about a serpant star and a brittle star, they are fine as well.

 

I thought about stray voltage. I can not feel any, I have a cut on my finger and usually if there is ANY i can feel it there. Right???

 

Open a window in my living room? I do open the sliding doors when I go out on the deck to smoke every couple hours, also is a very old and drafty house. If the point is to get more oxygen in I think we are fine there. Also my return creates a lot I think. see picture. I will add the bubble wall I have.

 

okay added a couple pics of sump and opened the window by the sump. Am adding bubble wall now.

 

Thanks, I never put 2 and 2 together with the low PH.

 

Well, that is done CB looks better, came out to eat . But Scooter blenny still has not moved, he is breathing.

 

Thanks!