Slight yellowing of fan leaves during flower

Hello all I just noticed the other day before watering my plants that a couple of them are starting to have some yellowing in the upper and larger fan leaves and just overall lightening in color from a dark green to a somewhat lighter green. Just wanted to get some advice before anything gets worse and potentially damages my harvest. I use fox farm nutes and happy frog soil particularly tiger bloom and did notice that I had been under feeding them and made sure to add about double the nutes to the tune of about 500-600 ppm and it appears that there hasn’t been any increased yellowing today. It looks like a nitrogen deficiency to me, but I just wanna make sure that it’s not a nutrient lockout. My pH is about 6.0-6.5 and my other plants appear to be doing fine! Temps we’re running high as well as in above 80 F, and have made appropriate changes to drop those into the mid to low 70s. I also added some cal mag in addition to the tiger bloom! Any feedback would be appreciated! Will post pictures and a video of course.
Here’s a better picture of what I was talking about! Can’t really tell if anything has progressed in the past couple of days, but you can see the large yellowish fan leave in the center of each plant. There are other leaves that are light green, but not as light as those fan leaves. I do believe it was from underfeeding, but just like to get a second opinion from the experts! I’m keeping a sharp eye on things so will continue to post of course if things worsen 👍🏻
Don’t get over concerned about the yellowing FF soils can have Cal-Mag issues in bloom if you don’t use big bloom with every water. Tiger bloom I used to use at 1/2 strength every third watering if things looked good. I added Cali magic through stretch and up potted twice ending up in five gallon smart pots. Did not use grow big at all plants did well. I did add mycos at transplant and a little bone meal to my final pot.