No one should be saying that a pH of 7.8 is too low. Anyone who claims that will get flamed. Your pH for soil should be 6.0-6.5, that is the accepted value, period.
It takes time for the plants to visually respond. Applying a foliar spray will give quicker results however.
So to answer your questions, I'd do both a foliar spray and a flush w 1/2 strength nutes.
For the foliar, I use a product w plant or fish protein hydrolysate and sea weed aka ascophyllum nodosum. I use floralicious plus by GH.
And the flush should be with nutes that have all macros and mircos in proper proportions. I use GH three part.
Thanks for the reply
Some have told me to use that splashing and washing plants Epsom salt? Is this a good idea or not? But I can use Plangron PHYT amine? If I understand you to mix 1/2 water mixture fertilizer (nutrients for growth) and wash plants? Then sprayed the leaves?