No reason you can't apply now, especially if your soil test shows a deficiency... but be aware that we don't necessarily shove nutrients down the turf's throat, at least not in any meaningful amount. If you have sufficient amounts of the necessary nutrient in the soil the turf will extract what it needs when it needs it. Loading it with too much of any one nutrient can cause other problems/reactions in the soil so more is not necessarily better.

 

The whole idea applying a potassium product during the summer is just youtube marketing.

 

Potassium can help with opening and closing the stomates that can help with water retention in the plant in turn "helping" with summer stress. That said, with a clay soil, that is provided the plant can obtain the K. Foliar app would be best.

If there is a deficiency, it would have to be very low to actually affect the plant.

 

I'm betting the label for Scotts says to wait 4-6+ weeks before reapplying. I would wait a few weeks (at least 4) before applying another fertilizer. Calculate how many lbs of Nitrogen you put down and determine if you should be using a 7-0-20 or not. I ran into a similar problem where I am K deficient and can't put down regular salts or sulfates (way over on calcium and sulfur), so I am stuck bi-weekly foliar feed with potassium acetate. Note this kind of treatment is considered late level 2 or level 3 lawn care (expensive/time consuming).

 

Foliar would be liquid. Cheapest would be soluble SOP. Not sure what other products are out there.

 

Also be careful - potassium will increase the use of nutrients like nitrogen and possibly reduce the uptake of magnesium, iron, zinc, and calcium. This could affect growth (stems/roots) negatively.
For liquid foliar feed, you are looking for potassium acetate. This generally will not feed the soil - only a supplemental boost via foliar applications.