You need N ( and lots of it ) not P.
And if doesn't say you can use it for foliar, I wouldn't.
I would use the one nute you can use as foilar and have a constant and steady regimen of foilar feeding until the pot is dry enough to water / nute again.
Place a plastic bag over the top of the pot to keep water from the foilar feeding out. It can add up quickly.
Last thing you plant needs is more moisture.
Just mix a batch and spray some of lower leaves heavily and wait to see if anything weird happens , Doubt it though as weak as that stuff is. Next day if all is well spray the whole plant, dry, spray. dry spray. dry, wait 20 minutes, put back under lights. Repeat.
If you do it right you should see results in a couple of days, darker green leaves, etc. If after a couple of days you don't see any real improvement , double or triple the nutes in the spray bottle..except cal mag.... Hopefully your pot will be dry by then.
But the faster you dry out the pot or repot the better.
When the roots are water logged they can't absorb nitrogen , so the leaves yellow from lack of nitrogen.
So if you don't repot, dry the hell out of it. ( So when you pick it up to check it's weight it should almost smack you in the face because it's so light ) Plants in veg can easily handle this.
Or if it droops ( you'll be able to tell the difference between curling and drooping.)
And before rewatering. pick the pot up and drop it from a few inches onto a hard surface or bang on the sides lightly. You need to break or loosen the soil without tearing the roots apart too much.
And not all pots dry out the same rate...I have plants in the same size pots be one or two difference in watering schedule, same soil, same strain, who knows ? I just water by weight anymore.
Once you get it dry and then back on track with nutes it should recover, you can still foilar for awhile if you need to.
Good luck.
