More questions about pH for (potted) citrus

[lemons4us]

I'm in Seattle, and during the cold months, I have several trees in an unheated greenhouse and others inside with lights. During this time, when I fertilize (using a watering can), I use vinegar to adjust the pH of our tap water - but during the warm months, when the trees are all outside, I water using the hose because it is so much easier to get them fully drenched. (In general, Seattle has dry summers). I'm wondering now if this could be an issue with why some of my trees aren't doing so well?  They are planted in 5-1-1.
Would there be any value in watering with city water, then re-watering with pH-adjusted water?

Am I worrying too much? Just trying to give them the best care. A couple of my trees aren't doing well, some are "ok" and others - mostly my lemons and limes, seem to be doing just fine.
Am I too stuck on pH? 

[JonW]

I also grow citrus in the Seattle area - I keep hardier varieties under an eave next to the house and cover if needed.  The rest goes in a greenhouse during winter.

I am probably not careful enough with water either and I don't check pH often enough.  (I just checked and they are between 6 and 7).  I'm not sure if it helps but I use an RV water filter outside whether via irrigation during summer or the regular hose during winter.

I suspect another issue we have is our low light levels in the winter - even if it is one of the few sunny days in the winter, they are short and the UV index is 0 or <1.    By late winter, nearly all my citrus had a few leaves that drop or turn yellow.  They are all looking better now.

I almost gave up on a Meyer lemon - it lost all but a few leaves a couple months ago.  A month ago, I pulled it out of its pot, replaced the soil (almost a sludge) with a new acidic mix, and ensured the very top of the root system wasn't smothered, and applied a foliar spray. Fortunately it has replaced much of the missing leaves, put on a lot of new growth, and the lemons are starting to change color.

[Vlad]

"Would there be any value in watering with city water, then re-watering with pH-adjusted water?"
No. pH of the water might have a brief affect on the soil medium pH but has little longer term effect due to the buffering capacity of the soil mix.

[lemons4us]

Thank you Vlad!